Purpose: To compare the results of arthroscopic rotator cuff repair and subacromial decompression in partial thickness rotator cuff tear (PTRCT) with those in full thickness rotator cuff tear (FTRCT). Subjects and method: Of the 46 patients who were rested of the rotator cuff tear based on the operational findings, 42 patients who were able to receive a serial follow-up for 2 years were selected as the study subjects. The average age of the patients at the time of the operation was 55 years, and the mean duration of the follow-up was 34 months. The subjects included 22 cases of PTRCT and 20 cases of FTRCT. In terms of rotator cuff repair, the average number of tendon to tendon repair (TTR) was 1 in both PTRCT and FTRCT, and that of tendon to bone repair (TBR) was 1 and 3 in PTRCT and FTRCT, respectively. The average number of use of suture anchor was 1 and 2 in PTRCT and FTRCT, respectively. The level of shoulder pain and function of the subjects were measured using shoulder functional evaluation score of American shoulder and elbow society (ASES score) at before and 2 years following the operation. Results: At the final follow-up following the operation, PTRCT group showed changes in scores from 7.2 to 0.9 on average pain score and 34 to 91 on ASES score, whereas FTRCT group showed changes in scores from 7.6 to 1.2 on pain score and 29 to 88 on ASES score. There were no significant differences between the two groups (P > 0.05). The average range of motion of shoulder significantly increased in both groups at the final follow-up in comparison with the pre-operative time point. The evaluation at the final follow-up showed that 93% of the total subjects showed good or excellent results, and 95％ showed satisfactory results from the procedure with regard to pain reduction and functional outcomes. Two cases of the 3 fair results were caused by acromioclavicular arthritis. Conclusion: It may be anticipated that arthroscopic rotator cuff repair and subacromial decompression may bring satisfactory post-operative outcomes in both PTRCT and FTRCT on pain relief and functional recovery. However, careful preoperative examination of the acromioclavicular joint is critical to avoid failures of these procedures.