Youth vaping and nicotine pouch use have risen as cigarette smoking declines, yet comparative evidence on their determinants remains limited. This study examined how socio-structural factors and an extended theory of planned behavior model predict nicotine vaping, nicotine pouch use, and cigarette smoking among Finnish youth. A survey of 1194 youth aged 15-25 assessed socioeconomic status, health literacy, theory of planned behavior belief-based constructs, intentions, behavior, and addiction. Nicotine pouches were viewed most favorably. Male gender associated more strongly with pouch use than vaping or smoking. Health literacy, but not socioeconomic status, predicted all behaviors. Affective attitudes were the strongest correlates across products; instrumental attitudes showed no effects. Friend norms exceeded family norms in influence, particularly for smoking. Affective attitudes and friend norms emerged as cross-cutting influences, while gender patterns and normative effects varied by product. Prevention strategies should address both shared and product-specific determinants.