diff --git a/DQM/GEM/src/GEMDQMBase.cc b/DQM/GEM/src/GEMDQMBase.cc
index b7735998888b4..8bac20ae31413 100644
--- a/DQM/GEM/src/GEMDQMBase.cc
+++ b/DQM/GEM/src/GEMDQMBase.cc
@@ -147,6 +147,7 @@ int GEMDQMBase::SortingLayers(std::vector<ME3IdsKey>& listLayers) {
 
 dqm::impl::MonitorElement* GEMDQMBase::CreateSummaryHist(DQMStore::IBooker& ibooker, TString strName) {
   std::vector<ME3IdsKey> listLayers;
+  listLayers.reserve(mapStationInfo_.size());
   for (auto const& [key, stationInfo] : mapStationInfo_)
     listLayers.push_back(key);
   SortingLayers(listLayers);
diff --git a/DQMOffline/Trigger/plugins/LepHTMonitor.cc b/DQMOffline/Trigger/plugins/LepHTMonitor.cc
index 94aef92131121..a85b51bf49943 100644
--- a/DQMOffline/Trigger/plugins/LepHTMonitor.cc
+++ b/DQMOffline/Trigger/plugins/LepHTMonitor.cc
@@ -360,9 +360,11 @@ void LepHTMonitor::bookHistograms(DQMStore::IBooker &ibooker, const edm::Run &iR
 
   //Convert to vfloat for picky TH1F constructor
   vector<float> f_ptbins;
+  f_ptbins.reserve(ptbins_.size());
   for (double ptbin : ptbins_)
     f_ptbins.push_back(static_cast<float>(ptbin));
   vector<float> f_htbins;
+  f_htbins.reserve(htbins_.size());
   for (double htbin : htbins_)
     f_htbins.push_back(static_cast<float>(htbin));
 
diff --git a/DQMOffline/Trigger/src/EgHLTOffHelper.cc b/DQMOffline/Trigger/src/EgHLTOffHelper.cc
index bf6e51e64da21..a8a31a7f625b5 100644
--- a/DQMOffline/Trigger/src/EgHLTOffHelper.cc
+++ b/DQMOffline/Trigger/src/EgHLTOffHelper.cc
@@ -256,6 +256,7 @@ int OffHelper::fillOffEleVec(std::vector<OffEle>& egHLTOffEles) {
     ele.setLooseCutCode(eleLooseCuts_.getCutCode(ele));
 
     std::vector<std::pair<TrigCodes::TrigBitSet, int> > trigCutsCutCodes;
+    trigCutsCutCodes.reserve(trigCuts_.size());
     for (auto& trigCut : trigCuts_)
       trigCutsCutCodes.push_back(std::make_pair(trigCut.first, trigCut.second.getCutCode(ele)));
     ele.setTrigCutsCutCodes(trigCutsCutCodes);
@@ -425,6 +426,7 @@ int OffHelper::fillOffPhoVec(std::vector<OffPho>& egHLTOffPhos) {
     pho.setLooseCutCode(phoLooseCuts_.getCutCode(pho));
 
     std::vector<std::pair<TrigCodes::TrigBitSet, int> > trigCutsCutCodes;
+    trigCutsCutCodes.reserve(trigCuts_.size());
     for (auto& trigCut : trigCuts_)
       trigCutsCutCodes.push_back(std::make_pair(trigCut.first, trigCut.second.getCutCode(pho)));
     pho.setTrigCutsCutCodes(trigCutsCutCodes);