Project Advancing Cessation of Tobacco in Vulnerable Indian Tobacco Consuming Youth (ACTIVITY) is a community-based group randomized intervention trial focused on disadvantaged youth (aged 10-19 years) residing in 14 low-income communities (slums and resettlement colonies) in Delhi, India. This article discusses the findings of Focus Group Discussions (FGDs) conducted to inform the development and test the appropriateness of Project ACTIVITY's intervention model. The findings of the FGDs facilitated the understanding of factors contributing to increased tobacco uptake and cessation (both smoking and smokeless tobacco) among youth in this setting. Twenty-two FGDs were conducted with youth (10-19 years) and adults in two urban slums in Delhi. Key findings revealed: (i) youth and adults had limited knowledge about long-term health consequences of tobacco use; (ii) socio-environmental determinants and peer pressure were important variables influencing initiation of tobacco use; (iii) lack of motivation, support and sufficient skills hinder tobacco cessation and (iv) active involvement of community, family, religious leaders, local policy makers and health professionals is important in creating and reinforcing tobacco-free norms. The results of these FGDs aided in finalizing the intervention model for Project ACTIVITY and guided its intervention development.