Objective: The objective was to investigate the presence of Helicobacter pylori with polymerase chain reaction in the sinonasal mucosa of patients with or without chronic rhinosinusitis (CRS). Study Design: A prospective clinical trial. Methods: Mucosal tissue samples were collected from ethmoid cells of 12 patients with CRS and the removed mucosal part of the middle concha of 13 patients with concha bullosa who were treated surgically in our institution. DNA extracted from these samples was used for the amplification of 16S ribosomal RNA gene of H pylori by nested polymerase chain reaction. Results: Helicobacter pylori DNA was detected in 4 of 12 patients with CRS, but it was not detected in patients with concha bullosa. Three of four patients with positive results for H pylori had gastroesophageal reflux-related complaints. Conclusions: It is possible to detect H pylori in the sinus mucosa of some patients with CRS. However, whether H pylori is a causative agent for CRS or a result of CRS is not known.