Purpose: The purpose of this study was to investigate long-term effects of physiotherapy program In patients with arthroscopic subacromial decompression (ASD). Material and methods: In a clinical prospective study, 33 consecutive patients who had undergone ASD and were resistant to conservative therapy and without full-thickness rotator Cuff tears were regularly evaluated up to six years. Postoperative follow-up was performed by an independent observer after the 5th week, 12th month and 6th year. Patients were assessed by Neer Shoulder Scoring system, the University of California at Los Angeles (UCLA) Shoulder Rating Scale, Visual Analogue Scale (VAS), isokinetic strength and goniometric measurements. Results: We found no differences in the clinical tests after six years (p>0.05). No differences were found between the three evaluation years in duration of sick leave and daily intake of analgesics (p>0.05). Six weeks after adjustment for ASD, the difference in improvement in overall Neer Score was 4.0 (95% confidence interval -2 to 11). The condition of patients with ASD who were given active treatments showed a significant incremental improvement in the sixth week, 12th month, and sixth year (p<0.05). Conclusion: All patients in this study improved with physiotherapy and rehabilitation. Physiotherapy and rehabilitation should be thought of as a first-line management method for patients with subacromial decompression.