Aims. (1) To develop a modular treatment program (ST/TST) for cannabis use disorders based on treatment packages and components that have been shown to be effective in previous US and Australian trials, and to adapt these material to the needs of our target population. (2) To demonstrate that this modular treatment package, implying motivational enhancement, cognitive-behavioral and psychosocial problem solving components is efficacious in comparison to a delayed treatment control (DTC) group. (3) Additionally, we test whether the targeted standardized treatment (TST) component tailored to address more specifically core problem areas results in superior short term (3-months) outcomes in these core domains as compared to the ST-group.