The concept of personality's constant individual traits and its significance, as well as implications for problems connected with choosing an occupation have been presented in the paper. Selected theories of occupational development have been analyzed from the concept viewpoint and certain traits of occupational personality presented by authors of occupational development theories have been confronted with constant individual traits of personality. Six types of J. Holland's occupational personality (i.e. realistic, investigative, artistic, social. industrious and conventional) have been analyzed. The number of kinds of each type has been calculated, after considering constant individual traits of personality. It has been concluded that due to constant individual traits of personality the processes connected with choosing an occupation should be highly individualised. Possibility of applying the concept to preparing a list of occupations and typology of occupational careers has been pointed out. Including constant individual traits of personality among basic determinants of occupational success has been suggested.