BACKGROUND-AIM:
Youth-focused tobacco prevention programs play a crucial role in shaping long-term health behaviours. “Agenti 00Sigarette – Missione LILT” is an evidence-based school intervention delivered to primary school classes in Milan between 2014–2015. After multiple evaluation phases (T0–T4), the present study aimed to (1) assess the long-term effects of the intervention 10 years later (T5) and (2) explore cognitive, emotional and behavioural representations concerning smoking among different subgroups through a qualitative follow-up (T6).

METHODS:
A mixed-method design was implemented. At T5, former participants now aged 18–20 completed an online survey. A total of 227 valid cases were collected and included in the analyses. The questionnaire assessed smoking behaviours, lifestyle indicators, nicotine dependence (Fagerström Test), psychological variables (knowledge, attitudes, cognitive representations, regulatory self-efficacy, deviant peers), emotions (PANAS-X) and memory/ appraisal of the intervention. Quantitative analyses were performed using SPSS. At T6, four focus groups (n=32; ≈8 participants each) were conducted, stratified by smoking status (smoker/non-smoker) and intervention exposure (experimental/control). Transcripts were analysed using thematic analysis.

RESULTS:
At T5, smoking and exposure to tobacco smoke were present but not pervasive. No significant differences emerged between experimental and control groups on smoking prevalence, while smokers—across groups—reported greater exposure to tobacco environments. Nicotine dependence levels were generally low. Knowledge about smoking risks was medium–high overall; however, participants in the experimental group showed more accurate responses on several key items. Their cognitive representations were more articulated and technically informed, particularly regarding harmful substances (e.g., carbon monoxide). Attitudes towards smoking were generally negative, especially among non-smokers. Memory of the program remained high after 10 years, with clear recall of core activities and overall evaluations were strongly positive. Thematic analysis from T6 indicated differences between groups in emotional associations, cognitive representations, and narratives related to smoking behaviour. Qualitative data revealed nuances not captured by the survey, highlighting contextual factors, peer influence dynamics and long-term reflections on the intervention experience.

CONCLUSIONS:
Findings suggest that the “Agenti 00Sigarette – Missione LILT” program maintains several long-term educational effects, particularly on knowledge and cognitive representations of smoking. While behavioural outcomes did not differ significantly between groups, both quantitative and qualitative evidence indicate a lasting imprint of the intervention on health-related awareness and emotional representations. Insights from T6 offer actionable indications for updating the program and strengthening future prevention strategies within school-based tobacco control initiatives.