The problem discussed in the article concerns nonassertive behaviour and its psychological consequences. In the next part of the paper the author presents many definitions of assertive behaviour, showing how the concept is understood by different psychologists. According to some authors, assertiveness is behaviour which is used in defence of individual’s right. Other psychologists emphasize in definition expressing feelings, attitudes, wishes and opinions in direct, decisive and honest way. There are also authors who define assertive behaviour as a right expression of any feelings, different from anxiety or a direct way of expressing thoughts, feelings and wishes in socially approved way. In the last part of the article there is a critical assessment of presented conceptions.