PURPOSE: To evaluate the various types and CT and MR imaging findings of choanal polyps. MATERIALS AND METHODS: We classified 42 cases of surgically proven choanal polyps into three types according to site of origin,and retrospectively analyzed imaging findings; in the case of antrochoanal polyps, particulr attention was givento extension of the lesion into the nasal cavity. We also determined whether MR imaging can provide moreinformation than CT. RESULTS: The antrochoanal polyp was the most common type( 33/42 : 78.6% ). Three cases ofchoanal polyps(7.1%) originated in the sphenoid sinus (sphenochoanal polyps), and while six( 14.3% ) did notinvolve the sinus( pure choanal polyps ). Thirty-six of 42 choanal polyps(85.7%) extended into either the choanaor nasopharynx. Three cases of antrochoanal polyps protruded through the middle meatus, and two into theoropharynx. The maxillary sinus component of an antrochoanal polyps extended more frequently through the accessoryostium( 29/33 ) than through the natural ostium. For delineating the stalk of an antrochoanal polyp, MR imagingwas not superior to CT. CONCLUSION: The most common type of choanal polyp is the antrochoanal, followed by purechoanal and sphenochoanal. CT and MR imaging can help identify lesion continuity between a choanal polyp and theparanasal sinus.