This research investigates the adoption factors of smartphones focusing on the differences of smartphone and feature phone users. We used Technology Acceptance Model (TAM) which incorporates service-oriented and device-oriented functional attributes as exogenous variables for a product-service system such as smartphones. In addition, Decision Tree (DT) and customer surveys were conducted. As a study results, we found that the service-oriented functional attributes - ‘wireless internet’ and ‘mobile applications’ - affect the adoption of smartphones regardless of users. However, the DT results revealed that the more important factor is 'mobile applications' to smartphone users but 'wireless internet' for feature phone users. In conclusion, we discovered that a strategy emphasis on the service-oriented attributes is needed for the adoption of smartphones.