This paper discusses a comparative and empirical research on critical success factors in IT project management and analyzes the effect of environmental idiosyncrasies on their relative importance. Based on a survey and some cases, the study extracted five common success factors in China and the USA. They are, namely, marketing skills, project strategy and process, management methodology and organization, project idea and creative team. It was found that firms in China put more emphasis on marketing skills and put less emphasis on other factors, in comparison with the USA. Meanwhile, it is revealed that firms in manufacturing sectors pay less attention to project ideas and more attention to management methodology and organization. Finally, it is found that smaller firms' competitive advantage relies more on marketing skills.