Six patients with chronically obstructed sinuses were examined with computed tomography (CT) and magnetic resonance (MR) imaging prior to surgical decompression. In all six patients, hypointense signal was present on all MR sequences despite CT evidence of the presence of high-attenuation material filling the sinus. At surgery, all specimens were viscid or pastelike with no evidence of hemorrhagic products as a cause for the MR findings. Sinonasal secretions may have a spectrum of MR signal intensity, ranging from hyperintense to signal void with all pulse sequences. These findings must be kept in mind when interpreting images of patients with suspected chronic sinusitis.