This study integrates consumer innovativeness (CI) and technological expertise (TE) in consumer attitudes and mobile commerce use (MCU) and introduces consumer consideration set size (CSS) as a moderator and a mediator of these relationships. Based on a survey sample of 577 Vietnamese consumers, it uses a structural equation modelling approach to test the hypotheses. The findings show that attitudes, CI, TE, and CSS have direct positive effects on MC use. The results also indicate a significant moderation effect between CI and TE on MCU. In particular, this study demonstrates that CSS is an important moderator and mediator in the relationships between attitudes, CI, TE, and MCU. The inclusion of mediation effects sharply increases the explained variance of MCU from 25.0% to 37.3%, with an effect size of 49.2%, compared with the model that only includes the direct effects. When the moderator effects are added, the explained variance of MCU increases to 51.7%, with an effect size of 38.6%, compared with the mediation model. Thus, the inclusion of mediation and moderation extends our understanding of the innovativenessattitude-behaviour relationship in explaining MCU. A deeper understanding of the size and structure of the consideration set is essential to obtain a higher consumer adoption rate and increase loyalty, especially for innovative consumers with high TE.