For one year we studied postoperative computed tomograms (CT) and intraoral radiographs for 29 patients with unilateral alveolar clefts. Interdental bone height and the bony boundary on the nasal side were assessed on intraoral films and compared with the evaluation by CT. Twenty-four cases had adequate interdental bone height as assessed by intraoral films. However, 10 of these 24 cases showed insufficient anteroposterior depth on CT. Two of the remaining five cases were also overestimated by the intraoral radiograph. All cases had sufficient bony boundary on the nasal side on intraoral radiography. However, CT showed that bone formation on the nasal side off two cases was significantly worse than that on the non-cleft side. Consequently, about 40% of surgical outcomes may be overestimated by intraoral radiographs. CT therefore seems to give a better assessment of the clinical outcome than intraoral radiographs and should be considered as an adjunct in difficult clinical cases.