Ukraine is one of the leading countries in Europe in terms of HIV prevalence, with injecting drug use being one of the main drivers of HIV transmission. Medication-assisted therapies (MAT) are the most effective means of preventing HIV transmission among people who inject drugs (PWID). As of January 1, 2022, 17,043 PWID in Ukraine were receiving MAT, which constitutes about 6% of the estimated number of PWID in the country. According to the official data, 6,002 MAT patients (35.2%) live with HIV, 5,736 (95.6%) of whom receive relevant HIV treatment. MAT in Ukraine is provided on the basis of more than 240 healthcare facilities, but not all of them offer psychosocial services to their patients. The aim of this study was to examine the access of MAT patients to psychosocial services on their MAT sites as well as to assess the role of access to such services at each stage of the HIV cascade. The source of data for this study was the national registry of all MAT patients in Ukraine. Descriptive statistics and logistic regression were used for the statistical analysis. The results of the analysis showed that patients' access to psychosocial services at MAT sites significantly improves the performance of the HIV service cascade at every stage: all MAT patients living with HIV are aware of their HIV-positive status; as for the access to appropriate HIV treatment – 97% and 95% of patients who have and do not have access to psychosocial services at their MAT sites receive antiretroviral therapy, respectively; and 83% and 67%, respectively, have an undetectable level of HIV viral load. Thus, access to psychosocial services at MAT sites significantly improves the HIV cascade indicators at each stage.