CONCLUSIONS The hypothesis that decongestants reduce the size of nasal polyps could not be verified. Decongestion is therefore recommended prior to nasal endoscopy, especially in polyp diagnosis, as it does not artificially change the size of the polyps. OBJECTIVE The role of nasal decongestants in nasal stuffiness is well established and their action is well known. Decongestants are also used prior to nasal endoscopy to achieve a better view of the nasal cavity in order to diagnose polyps. The question is whether this decongestion invalidates the estimation of polyp size in clinical and scientific practice. The aim of this study was to evaluate possible effects of topical decongestants on polyp extension in patients with nasal polyposis. METHODS The effect of the decongestants nafazoline and epinephrine on nasal polyp size was assessed by means of a double-blind, placebo-controlled randomized study. A sensitive endoscopic scoring system, lateral imaging, was used to assess the size and extension of the nasal polyps. RESULTS No significant effect of decongestion on polyp size could be found for either treatment.