The report highlights the domains where project managers have more difficulties and lack of professional skills. The results of project simulations carried out by more than 8000 project managers and students of business schools around Europe show areas of common pitfalls. The same analysis is made for 500 PMP examination preparation sessions. Business simulation provides an opportunity for data mining and analysis because participants meet similar situations. The methodology is based on study the knowledge areas, process groups and competences, where the difference between the participants and experts opinions is the greatest. The analysis highlights the major shortcomings of project delivery, decision making, and risk reaction and lists the common mistakes made by managers. Further, it demonstrates that managers’ proactive behaviour and risk prevention attitudes as well as investing into communication and team development result in better project performance.