To reproduce: Add image like this: void button_Click1(object sender, EventArgs e) { Section section = new Section(); Paragraph paragraph = new Paragraph(); ImageInline image; Telerik.WinControls.RichTextEditor.UI.Size size = new Telerik.WinControls.RichTextEditor.UI.Size(236, 50); using (MemoryStream ms = new MemoryStream()) { System.Drawing.Image.FromFile(@"C:\img\delete.png").Save(ms, System.Drawing.Imaging.ImageFormat.Png); image = new ImageInline(ms, size, "png"); } paragraph.Inlines.Add(image); section.Children.Add(paragraph); this.radRichTextEditor1.Document.Sections.Add(section); } Workaround: Manually update the layout: this.radRichTextEditor1.UpdateEditorLayout();