PURPOSE: Depressed colorectal cancer is a newly recognized colorectal cancer. It has the characteristics of rapid growth and early invasion of the submucosa. Accordingly, recognition of that lesion is important. However, it is still rarely detected in Korea. This study was designed to evaluate the characteristics of depressed colorectal neoplastic lesions. METHODS: We experienced 22 cases of depressed neoplastic lesions from January 1997 to December 1998. All of them were detected by performing colonoscopy. Among them, 6 were early colorectal cancers. The twenty-two cases accounted for 1.3% of all neoplastic lesions but advanced colorectal cancers encountered during the same period, and the six accounted for 6.6% of all early colorectal cancers during that period. We reviewed and analyzed those 22 lesions with respect to their clinicopathologic characteristics, especially size and histology. RESULTS: The most common age group was the 6th decade. The male-to-female ratio was 2.7 to 1. The predilection of sites were the descending colon, the transverse colon, and the sigmoid colon in that order. The most common size was 3~4 mm, 9 lesions (40.9%) and the next was 5~6 mm, 7 lesions (31.8%). Twenty lesions (90.9%) were 8 mm or smaller in size. The overall malignancy rate was 27.3% (6/22), comprising 9.1% (2/22) for mucosal cancers, and 18.2% (4/22) for submucosal ones. The two lesions which were larger than 10 mm were submucosal cancers. Endoscopic mucosal resection (EMR) was the most common type of treatment, accounting for 59.1%. Two submucosal cancers and one mucosal cancer were operated on without any endoscopic treatment. That one mucosal cancer had initially been suspected of being a submucosal one upon endoscopic examination. There were neither complications nor recurrences during the average 10-month follow-up. CONCLUSIONS: The target for detecting and treating depressed colorectal cancer should be lesions below 10 mm in size, and the treatment of choice should be EMR.