OBJECTIVES: To explore real-world outcomes and costs of patients treated with risperidone long-acting injection (RLAI) in New Zealand. METHODS: A mirror-image retrospective study was conducted comparing outcomes and costs 12 months post- versus 12 months pre-initiation of RLAI in adults approved for treatment between October 2005-October 2006 in 5 health services. Continuation rates, compulsory treatment status, psychiatric hospitalisation (admission number, bed-stay and cost), and treatment data were collected for twelve months on either side of first RLAI prescription. Hospitalisation costs were valued using estimates for cost/admission and cost/bed-day ($NZ, 2009 values). RESULTS: 58.3% of patients remained on RLAI 12 months after initiation. The average number of admissions for the total study population was significantly less in the post-RLAI period (1.38 vs 0.61, p<0.001) but average length of bed-stay increased (37.2 vs 53.3 days, p<0.001) as did compulsory treatment use. Overall bed-nights increased by 6877 in the post-RLAI period driven mostly by those who discontinued treatment. Patients who continued RLAI had fewer admissions and days in hospital post-RLAI compared to patients who discontinued RLAI in the first year. The reduction in total hospital admission rates between the two treatment periods was significantly greater in continuation group and mean difference in bed-days between the two treatment periods was significantly less for continuers (5.4 vs. 31.1 days, p<0.001).  Applying a cost/admission, hospitalisation costs reduced by approximately $NZ1 million in the post RLAI-period. Applying a daily hospitalisation cost resulted in an increase of approximately $NZ3.5 million in the post-RLAI period. CONCLUSIONS: study suggests that patients have reduced hospital admissions but longer bed-stay after starting RLAI. Longer admissions were driven by those that discontinued treatment and continuation was associated with improved resource and cost outcomes compared to those who discontinued.  These findings have potential implications for payers, providers and patients, requiring further investigation over a longer timeframe.