The Korean Standard Classification of Diseases (KCD), which reflects the International Classification of Diseases (ICD), is a fundamental coding system for the diagnosis of colorectal epithelial tumors. The KCD coding of colorectal lesions is entirely up to the clinician and is based on pathologic reports. However, coding discrepancies have arisen among physicians using the KCD and pathologists using the ICD for Oncology-3 (ICD-O-3). The Korean Society of Pathologists recently proposed a standardized pathology-reporting format and guidelines for the coding of colorectal cancer to decrease these discrepancies among pathologists. However, ICD and ICD-O are simple classification codes based on pathologic reports, and are neither intended nor suitable for indexing of distinct clinical entities. For appropriate diagnostic coding using the KCD, a corrected coding principle based upon pathologic reports is required, and unified coding between KCD and ICD-O is necessary. A standardized pathologic report format and communication with understanding between physicians and pathologists should be established. Additionally, the private medical insurance system for colorectal cancer should be revised to reduce conflicts among patients, clinicians, and insurance companies over the medical coding system.