To reproduce: private void Form1_Load(object sender, EventArgs e) { this.productsTableAdapter.Fill(this.nwindDataSet.Products); this.radGridView1.EnableFiltering = true; this.radGridView1.ShowHeaderCellButtons = true; this.radGridView1.ShowFilteringRow = false; this.radGridView1.Columns["UnitPrice"].FormatString = "{0:$#,###0.00;-$#,###0.00;$0.00}"; } Workaround: in order to format the cells, use the CellFormatting event. As to the filter popup, use the following approach: this.radGridView1.FilterPopupInitialized += radGridView1_FilterPopupInitialized; private void radGridView1_FilterPopupInitialized(object sender, Telerik.WinControls.UI.FilterPopupInitializedEventArgs e) { RadListFilterPopup popup = e.FilterPopup as RadListFilterPopup; if (popup != null) { popup.MenuTreeElement.TreeView.NodeFormatting -= TreeView_NodeFormatting; popup.MenuTreeElement.TreeView.NodeFormatting += TreeView_NodeFormatting; } } private void TreeView_NodeFormatting(object sender, TreeNodeFormattingEventArgs e) { decimal price; if (decimal.TryParse(e.Node.Text, out price)) { e.NodeElement.ContentElement.Text = string.Format("{0:$#,###0.00;-$#,###0.00;$0.00}", price); } }