In international projects, firms need to cope with the challenges posed by institutional differences. Existing studies focus on the perspective of risk management and propose corresponding strategies to deal with the fact that institutional differences can cause great trouble to the implementation of international projects. However, it has not been systematically studied whether influences of different types of institutional differences on different implementation issues are of similar degree. Based on the data of the international projects of Chinese construction firms collected by questionnaire and interviews, the influences of different institutional differences on project implementation are analyzed. The results show that the influence of technical standards difference on design, procurement and construction issues is the most prominent. Cultural difference also has some effects on project implementation. Difference in laws and regulations, however, has no statistically significant influence on project implementation issues. Chinese construction firms should pay more attention to the standards and cultural factors when dealing with institutional differences.