Background: Abiraterone acetate (AA) is a potent, selective androgen (CYP17) biosynthesis inhibitor, which showed to improve overall survival in mCRPC pts progressing after docetaxel. Few data are available concerning the clinical outcome of AA treatment in mCRPC in terms of the duration of prior androgen deprivation therapy (ADT). In this retrospective analysis we assessed the PFS and OS in patients affected with mCRPC according to the duration of ADT. Methods: We retrospectively reviewed the clinical data of pts affected by mCRCP progressive after chemotherapy who received AA (1000 mg/d) plus prednisone (5 mg/twice daily). A total of 189 pts were included in the analysis, 71 received AA with ADT duration<12 months (Group A) and 118 received AA with ADT duration ≥ 12 months (Group B). Patient characteristics’ in the two treatment groups (A VS B) were: median age: 75 vs 69 years, Gleason score ≥7: 96% vs 92%; median PSA at AA start 47 (range 36-2130) vs 32 (range 85-2100), No of metastatic sites: 1 : 70% vs 75% ;bone only 50% vs 47%, visceral disease alone: 3% vs 5%; symptomatic disease : 58% vs 40% (p 0.02); median number of prior docetaxel courses: 6 in both groups; second-line cabazitaxel:14% in both groups, bisphosphonates concomitant treatment 66% vs 52.5% (p:0.21). No difference in radical prostatectomy or radiation therapy were evidenced Results: At a median follow-up of 8.5 months (range 1-51) the median progression-free survival (PFS) and the median overall survival (OS) were 10 months (95% CI: 7-13) and 26 months (95% CI: 17-35) respectively in all mCRPC. Group B patients had a statistically significant longer PFS (13 vs 7 months, p=0.009) and OS (28 vs 17 months, p=0.03 months). The median decrease in the PSA level > 50% was observed in 50 % of pts in both groups. AA was well tolerated and no relevant toxicity were observed Conclusions: This retrospective analysis showed a benefit in terms of PFS and OS in group B patients, our finding might be related to the best prognostic factors of patients in group B (less symptomatic).