diff --git a/Detectors/Upgrades/ALICE3/TRK/macros/test/CMakeLists.txt b/Detectors/Upgrades/ALICE3/TRK/macros/test/CMakeLists.txt
index 54e42c6857249..33d1b4a5afdc6 100644
--- a/Detectors/Upgrades/ALICE3/TRK/macros/test/CMakeLists.txt
+++ b/Detectors/Upgrades/ALICE3/TRK/macros/test/CMakeLists.txt
@@ -49,3 +49,11 @@ o2_add_test_root_macro(CheckClusters.C
                                              O2::TRKBase
                                              O2::TRKSimulation
                        LABELS trk COMPILE_ONLY)
+
+o2_add_test_root_macro(postClusterSizeVsEta.C
+                       PUBLIC_LINK_LIBRARIES O2::DataFormatsTRK
+                                             O2::SimulationDataFormat
+                                             O2::Framework
+                                             O2::TRKBase
+                                             O2::TRKSimulation
+                       LABELS trk COMPILE_ONLY)
diff --git a/Detectors/Upgrades/ALICE3/TRK/macros/test/postClusterSizeVsEta.C b/Detectors/Upgrades/ALICE3/TRK/macros/test/postClusterSizeVsEta.C
new file mode 100644
index 0000000000000..47beaf36f2957
--- /dev/null
+++ b/Detectors/Upgrades/ALICE3/TRK/macros/test/postClusterSizeVsEta.C
@@ -0,0 +1,199 @@
+// Copyright 2019-2026 CERN and copyright holders of ALICE O2.
+// See https://alice-o2.web.cern.ch/copyright for details of the copyright holders.
+// All rights not expressly granted are reserved.
+//
+// This software is distributed under the terms of the GNU General Public
+// License v3 (GPL Version 3), copied verbatim in the file "COPYING".
+//
+// In applying this license CERN does not waive the privileges and immunities
+// granted to it by virtue of its status as an Intergovernmental Organization
+// or submit itself to any jurisdiction.
+
+/// \file postClusterSizeVsEta.C
+/// \brief A post-processing macro to draw average cluster size vs eta
+
+#if !defined(__CLING__) || defined(__ROOTCLING__)
+#include <iostream>
+#include <TCanvas.h>
+#include <TFile.h>
+#include <TH1F.h>
+#include <TH2F.h>
+#include <TNtuple.h>
+#include <TString.h>
+#include <TTree.h>
+#include <TROOT.h>
+#include <TStyle.h>
+#include <TLegend.h>
+#include <TProfile.h>
+#endif
+
+using namespace std;
+
+// ### required input file: CheckClusters.root, which is the output of CheckClusters.C macro
+void postClusterSizeVsEta(const std::string& strFileInput = "CheckClusters.root")
+{
+  gStyle->SetOptStat(0);
+
+  TFile* fileInput = new TFile(strFileInput.c_str());
+  TTree* tree = (TTree*)fileInput->Get("ntc");
+  std::cout << "Opened tree: " << tree->GetName() << ", entries = " << tree->GetEntries() << std::endl;
+
+  // set branch addresses
+  Float_t event;
+  Float_t mcTrackID;
+  Float_t hitLocX, hitLocZ;
+  Float_t hitGlobX, hitGlobY, hitGlobZ;
+  Float_t clusGlobX, clusGlobY, clusGlobZ;
+  Float_t clusLocX, clusLocZ;
+  Float_t rofFrame;
+  Float_t clusSize;
+  Float_t chipID;
+  Float_t layer;
+  Float_t disk;
+  Float_t subdet;
+  Float_t row, col;
+  Float_t pt;
+
+  // set branch addresses
+  tree->SetBranchAddress("event", &event);
+  tree->SetBranchAddress("mcTrackID", &mcTrackID);
+  tree->SetBranchAddress("hitLocX", &hitLocX);
+  tree->SetBranchAddress("hitLocZ", &hitLocZ);
+  tree->SetBranchAddress("hitGlobX", &hitGlobX);
+  tree->SetBranchAddress("hitGlobY", &hitGlobY);
+  tree->SetBranchAddress("hitGlobZ", &hitGlobZ);
+  tree->SetBranchAddress("clusGlobX", &clusGlobX);
+  tree->SetBranchAddress("clusGlobY", &clusGlobY);
+  tree->SetBranchAddress("clusGlobZ", &clusGlobZ);
+  tree->SetBranchAddress("clusLocX", &clusLocX);
+  tree->SetBranchAddress("clusLocZ", &clusLocZ);
+  tree->SetBranchAddress("rofFrame", &rofFrame);
+  tree->SetBranchAddress("clusSize", &clusSize);
+  tree->SetBranchAddress("chipID", &chipID);
+  tree->SetBranchAddress("layer", &layer);
+  tree->SetBranchAddress("disk", &disk);
+  tree->SetBranchAddress("subdet", &subdet);
+  tree->SetBranchAddress("row", &row);
+  tree->SetBranchAddress("col", &col);
+  tree->SetBranchAddress("pt", &pt);
+
+  // Some QA histograms
+  TH1F* hPt = new TH1F("hPt", "p_{T};p_{T};Entries", 100, 0., 10.);
+  TH1F* hClusSize = new TH1F("hClusSize", "Cluster size;clusSize;Entries", 20, 0., 20.);
+  TH1F* hLayer = new TH1F("hLayer", "Layer;layer;Entries", 20, -0.5, 19.5);
+  TH1F* hDxGlob = new TH1F("hDxGlob", "clusGlobX - hitGlobX;#DeltaX [global];Entries", 200, -1., 1.);
+  TH1F* hDzGlob = new TH1F("hDzGlob", "clusGlobZ - hitGlobZ;#DeltaZ [global];Entries", 200, -1., 1.);
+  TH2F* hHitXY = new TH2F("hHitXY", "Hit global XY;hitGlobX;hitGlobY", 200, -20., 20., 200, -20., 20.);
+  TH2F* hClusVsHitX = new TH2F("hClusVsHitX", "clusGlobX vs hitGlobX;hitGlobX;clusGlobX", 200, -20., 20., 200, -20., 20.);
+
+  // histograms for cluster size vs eta for each barrel layer:
+  const int nLayers = 11;
+  TH2F* hClustSizePerLayerVsEta[nLayers];
+  for (int i = 0; i < nLayers; i++) {
+    hClustSizePerLayerVsEta[i] = new TH2F(Form("hClustSizePerLayerVsEta_Lay%d", i), Form("Cluster size vs eta for layer %d;#eta;Cluster size", i), 200, -5, 5, 101, -0.5, 100.5);
+  }
+
+  // Loop over entries
+  const Long64_t nEntries = tree->GetEntries();
+  for (Long64_t i = 0; i < nEntries; ++i) {
+    tree->GetEntry(i);
+
+    // Fill QA histograms
+    float dXGlob = clusGlobX - hitGlobX;
+    float dZGlob = clusGlobZ - hitGlobZ;
+    hPt->Fill(pt);
+    hClusSize->Fill(clusSize);
+    hLayer->Fill(layer);
+    hDxGlob->Fill(dXGlob);
+    hDzGlob->Fill(dZGlob);
+    hHitXY->Fill(hitGlobX, hitGlobY);
+    hClusVsHitX->Fill(hitGlobX, clusGlobX);
+
+    // cls size vs eta:
+    float clustR = sqrt(clusGlobX * clusGlobX + clusGlobY * clusGlobY);
+    float clustPhi = atan2(clusGlobY, clusGlobX);
+    float clustTheta = atan2(clustR, clusGlobZ);
+    float clustEta = -log(tan(clustTheta / 2));
+
+    // !!! important: to avoid VD layers (numeration for ML starts from 0, while VD layers are also numbered as 0,1,2)
+    if (clustR > 5) // cm
+      hClustSizePerLayerVsEta[(int)layer + 3]->Fill(clustEta, clusSize);
+    else if (layer < 3) // VD layers
+      hClustSizePerLayerVsEta[(int)layer]->Fill(clustEta, clusSize);
+
+    // progress print
+    if ((i + 1) % 200000 == 0) {
+      std::cout << "Processed " << (i + 1) << " / " << nEntries << " entries" << std::endl;
+    }
+  }
+
+  // Save histograms to file
+  TFile* fout = TFile::Open("clusterSizes_vs_eta.root", "RECREATE");
+  hPt->Write();
+  hClusSize->Write();
+  hLayer->Write();
+  hDxGlob->Write();
+  hDzGlob->Write();
+  hHitXY->Write();
+  hClusVsHitX->Write();
+
+  // draw some QA histograms
+  TCanvas* c1 = new TCanvas("canv_clusters_QA", "Clusters QA", 1200, 800);
+  c1->Divide(2, 2);
+  c1->cd(1);
+  hPt->Draw();
+  c1->cd(2);
+  hClusSize->Draw();
+  c1->cd(3);
+  hDxGlob->Draw();
+  c1->cd(4);
+  hHitXY->Draw("COLZ");
+
+  int colors[] = {kRed, kBlue + 1, kMagenta + 1,
+                  kRed, kBlue + 1, kMagenta + 1,
+                  kCyan + 1, kGray + 2, kRed, kBlue, kMagenta + 1, kCyan, kAzure + 1, kOrange - 9, kRed + 2, kBlue + 2, kMagenta + 2};
+
+  TCanvas* canv_clsSize_vs_eta[nLayers];
+  TProfile* profPerLayerVsEta[nLayers];
+  for (int i = 0; i < nLayers; i++) {
+    canv_clsSize_vs_eta[i] = new TCanvas(Form("canv_clsSize_vs_eta_Lay%d", i), Form("Cluster size vs eta for layer %d", i), 800, 600);
+    hClustSizePerLayerVsEta[i]->Draw("COLZ");
+    gPad->SetLogz();
+    profPerLayerVsEta[i] = hClustSizePerLayerVsEta[i]->ProfileX();
+    profPerLayerVsEta[i]->SetLineColor(colors[i]);
+    profPerLayerVsEta[i]->SetMarkerColor(colors[i]);
+    profPerLayerVsEta[i]->SetMarkerStyle(i < 8 ? 20 : 24);
+    profPerLayerVsEta[i]->SetTitle(";#eta;#LTcluster size#GT");
+    profPerLayerVsEta[i]->DrawCopy("same");
+
+    hClustSizePerLayerVsEta[i]->Write();
+    profPerLayerVsEta[i]->Write();
+  }
+
+  // ### canvas with profiles for 3 VD layers
+  TCanvas* canv_av_clsSize_vs_eta_VD_layers = new TCanvas("canv_clsSize_vs_eta_VD_layers", "Cluster size vs eta for VD layers", 800, 600);
+  TLegend* legLayersVD = new TLegend(0.3, 0.72, 0.65, 0.89);
+  for (int i = 0; i < 3; i++) {
+    profPerLayerVsEta[i]->GetYaxis()->SetRangeUser(0., 60.);
+    profPerLayerVsEta[i]->DrawCopy(i == 0 ? "P" : "P same");
+    legLayersVD->AddEntry(profPerLayerVsEta[i], Form("VD layer %d", i), "P");
+  }
+  legLayersVD->Draw();
+  gPad->SetGrid();
+  canv_av_clsSize_vs_eta_VD_layers->SaveAs("clsSize_vs_eta_VD_layers.png");
+  canv_av_clsSize_vs_eta_VD_layers->Write();
+
+  // ### canvas with profiles for MLOT layers
+  TCanvas* canv_av_clsSize_vs_eta_MLOT_layers = new TCanvas("canv_clsSize_vs_eta_MLOT_layers", "Cluster size vs eta for MLOT layers", 800, 600);
+  TLegend* legLayersMLOT = new TLegend(0.3, 0.52, 0.65, 0.89);
+  for (int i = 3; i < nLayers; i++) {
+    profPerLayerVsEta[i]->GetYaxis()->SetRangeUser(0., 12.5);
+    profPerLayerVsEta[i]->GetXaxis()->SetRangeUser(-3.5, 3.5);
+    profPerLayerVsEta[i]->DrawCopy(i == 3 ? "P" : "P same");
+    legLayersMLOT->AddEntry(profPerLayerVsEta[i], Form("MLOT layer %d", i), "P");
+  }
+  legLayersMLOT->Draw();
+  gPad->SetGrid();
+  canv_av_clsSize_vs_eta_MLOT_layers->SaveAs("clsSize_vs_eta_MLOT_layers.png");
+  canv_av_clsSize_vs_eta_MLOT_layers->Write();
+}
\ No newline at end of file