Purpose: To evaluate the usefulness of arthroscopic decompression and miniopen repair that was related with large and massive sized full thickness rotator cuff tear and assess clinical result. Materials and Methods: Twenthy-nine cases of miniopen repaired full thickness tear of rotator cuffs that arthroscopically decompressed were studied. From October 1998 to December 2004 we have analysed 29 repairs of large and massive sized FTRCT, the average age 44 ($32{sim}71$) years old, mean follow-up was 34 ($12{sim}84$) months. We analyzed the results statistically by paired t-test. Results: Postoperative VAS of pain improved average 7.0 to 1.7, UCLA score improved 13.7 to 31.9, ADL improved 11.3 to 25.3 respectively (all, P=0.000). Twenty five cases(82.8%) of the patients showed excellent & good results at the final follow-up. The satisfied rate was 26 cases(89.7%). Conclusions: Arthroscopic decompression and miniopen repair in large and massive sized full thickness rotator cuff tears are effective surgical methods.