OBJECTIVE To explore the proper methodology to treat cubitus varus deformity in adults with lateral closing wedge osteotomy. METHODS The clinical data of 20 adult patients with post-traumatic cubitus varus deformity who underwent lateral closing wedge osteotomy and were followed up for 40 months on average were analyzed. RESULTS twenty-seven of the 28 patients showed excellent heal, and one case of delay in healing occurred. Eighteen elbow joints were in a neutral position, 6 were slightly varus, and 4 were varus. Tardy ulnar nerve palsy occurred in 5 cases. Reduction of elbow flexion was 11 degrees, even more than 20 degrees in 5 cases. Four patients were able to flex their elbows by 120 degrees or less. The reduction of extension was 3.4 degrees on average. Two patients showed failure of internal fixation, Kirshner wires were used in both of which. CONCLUSIONS Exact pre-operative planning of osteotomy, minimal injury to the soft tissues, proper dealing of the ulnar nerve, and stable internal fixation are the key factors that improve the function of elbow joint after the lateral closing wedge osteotomy and reduce the post-operative complications.