Smartphones are becoming the mainstream mobile devices used by Hong Kong residents. The popularity of smartphones has led to the emergence of a new way of trading in financial securities and products - so called: mobile stock trading. This new technology has several attractive features that have driven this new market forward. Investors can place orders at anytime and anywhere without any geographic restriction as long as they can access the internet. By using the Diffusion of Innovation model (DOI) and related literature, we found that three factors: perceived usefulness, trialability and observability - contribute to the determination of customer attitudes in adopting mobile stock trading. The results revealed practical implications for the future development and implementation of mobile stock trading.