Due to the development of information technology, music piracy has become an escalating problem. This study attempts to employ the theory of planned behavior (TPB) and the social identity theory to investigate the antecedents of downloading pop music illegally from the Internet, the relationship between the intention to illegally download music and the intention to buy music, and the moderating effects of idolatry. Data were collected from 350 teenagers in Northern Taiwan through questionnaire interviews conducted in city cen-ters where teenagers gather. The results of partial least squares (PLS) analyses reconfirm the explanatory power of the TPB model with regard to the pop music illegal downloading behavior. However, it is interesting to note that the intention to illegally download music does not have a significant influence on the intention to buy music. This finding contradicts our common intuitions. Further analyses also reveal that idolatry moderates the relation-ship between the intention to illegally download music and the intention to buy music. For teenagers with high idolatry, a higher music downloading intention results in a lower buying intention. One possible explanation is the price of music CDs. Several interviews were also held to verify our results. Implications and a discussion are then provided.