BACKGROUND/AIMS: In line with Self-determination Theory, individuals who feel they are able to adopt new behaviors autonomously, and who perceive their social environment as supportive of their autonomy and confident in their competencies, are more likely to engage in sustainable behavioral change over time. We aimed to study the impact of an educational intervention, which has already shown its effectiveness in reducing transmission-risk behaviors and injection-related complications among drug users (Roux et al., 2016), on three psychosocial factors (PSF) involved in initiating and maintaining new health behaviors over time, as follows: A) self-regulation of behaviors (autonomous vs. controlled regulation); B) perceived competence in adopting new behaviors (a feeling of being able or unable to adopt new behaviors) and C) perceived autonomy support (social environment perceived by drug users as supportive of autonomy vs. controlling). METHODS: This non-random clustered intervention study was conducted in 9 intervention groups (programs offering the intervention) and 8 control groups (programs not offering it). Each participant was followed up through a phone interview at enrolment, at 6 months and 12 months. Of the 271 participants, 113 received at least one educational session in the first six months. We used the "Health-Care Self-Determination Theory Questionnaire" to assess the impact of this intervention on the development of self-regulation, perceived competence and perceived autonomy support. RESULTS: Participants exposed to the intervention at least once were associated with a higher level of perceived competence and perceived autonomy support at M12. However, the intervention did not impact self-regulation (either autonomous or controlled). In addition, the study revealed that other factors, such as gender, age, drug use patterns and participants' healthcare pathways, also have an impact on these PSF. CONCLUSIONS: This educational intervention significantly increases patients' perceived competence but has no impact on the factors specifically involved in maintaining new behaviors over time. This study also highlights the existence of user profiles whose socio-demographic characteristics, use patterns and care pathways can influence these FPS involved in motivation to change and maintain new health behaviors over time.