AIM: To determine the computed tomography (CT) and magnetic resonance imaging (MRI) features of leiomyoma of the sinonasal cavity. MATERIALS AND METHODS: Six patients with histology-proven leiomyomas in the sinonasal cavity were retrospectively reviewed. All six patients underwent CT and three patients also underwent MRI. The following imaging features were reviewed: size, margin, CT attenuation, MRI signal intensity, and lesion extent. In addition, the time-intensity curve (TIC) of dynamic contrast-enhanced (DCE) MRI and diffusion-weighted imaging (DWI) were analysed in two patients. RESULTS: All leiomyomas had well-defined margins. The mean size was 36 mm (range 20-51 mm). On unenhanced CT, the lesions appeared isodense to cerebral grey matter in four (67%) and slightly hypodense in two (33%) patients. Leiomyomas appeared isointense On T1-weighted imaging (WI) and slightly hyperintense on T2WI in three patients. The lesions showed moderate contrast enhancement. Two patients underwent DCE MRI, and the TIC showed a rapidly enhancing and stow washout pattern. The mean apparent diffusion coefficient (ADC) value were 1.66 x 10(-3) mm2/s and 1.78 x 10(-3) mm(2)/s for the two lesions, respectively. CONCLUSIONS: Welt-defined, homogeneous, expansile masses without bony erosion are typical features of leiomyoma. Althrough rare, this entity should be included in the differential diagnosis of benign tumours in this region. (C) 2009 The Royal College of Radiologists. Published by Elsevier Ltd. All rights reserved.