The central question in the research is based on the personality differences between professional athletes and regular persons. The thesis focus on which personality traits of a professional athlete predicts career success and leadership effectiveness. The goal of the research is to investigate the personality differences between these two groups. The professional athletes and regular persons filled in a questionnaire based on the Big Five model and a scale of leadership effectiveness. The results are based on questionnaires, from regular persons and from professional athletes. This research shows that professional athletes score higher on extraversion, openness to experience, agreeableness and leadership effectiveness, while professional athletes tend to score lower on consciousness and emotional stability than regular persons. Only the difference on extraversion and consciousness is significant, for the other three traits there is not enough evidence.