OBJECTIVES: Advances in the treatment of opioid use disorder (OUD) have seen the development of long-acting injectable opioid substitutes which could improve outcomes for people with OUD. However, comparative quantitative analysis of individual outcomes is lacking. The present study sought to investigate factors associated with prescribing long-acting injectable buprenorphine (LAIB), and changes in outcome variables compared with oral medication for OUD. DESIGN: Cross-sectional retrospective analysis of electronic health records. SETTING: Community substance use treatment service Via. Six sites shared their data between 15 August 2022 and 15 August 2023. PARTICIPANTS: Anonymised data were extracted for 235 people receiving LAIB and 266 people receiving oral medication for OUD. PRIMARY AND SECONDARY OUTCOMES: Prescribing data, sociodemographic information (age, sex, indices of multiple deprivation decile of individual's residence, primary and secondary substance, number of previous treatment episodes, employment and ethnicity) and treatment outcome profiles (substance use, physical and mental health, quality of life, employment) were extracted and analysed. To examine predictors of receiving LAIB (vs medication for OUD), we conducted logistic regression including the demographic predictors. Psychological health, physical health and quality of life scores were analysed using Welch's t-tests. RESULTS: LAIB was associated with positive changes in quality of life between the first and last assessments. Demographic and situational factors were predictors of LAIB initiation, indicating the potential for increasing health inequalities in substance use treatment. CONCLUSIONS: LAIB is associated with changes in quality of life over a 1-year period. Further research is needed to investigate the aetiology of improved well-being and outcomes over time.