Motivation for work is crucial for the success of modern organizations. Factors that influence the motivation for work are numerous, and their importance is changing. The hierarchy of motivational factors was researched in different time frames and different cultures. In addition the influence of individual characteristics of employees has also been researched. The paper presents a survey of attitudes about the influence of the above mentioned factors on motivation for the work of professional members of the Serbian Armed Forces. The data were collected by anonymous survey of a suitable sample of 1929 members of the Serbian Army during 2010, 2018 and 2020. The questionnaire developed for research consists of a scale of 18 and 16 motivational factors. The 18item scale has a high level of internal consistency (a =0.909/N1) as well as the 16-item scale (a=0.877/N2) and (a=0.829/N3). According to the study results, the hierarchy of motivational factors was constructed: 1) Love for work, 2) Interesting work, 3) Good interpersonal relations, 4) Correct attitude of the manager, 5) Self-affirmation, 6) Success in work, 7) Security of employment, 8) Information sharing, 9) Responsible work, 10) Taking part in decision making, 11) Fair distribution of work, 12) Salary level, 13) Receiving praises, 14) Independence, 15) Possibility for postgraduate training, 16) Awards, 17) Delegation of power, and 18) Criticism. The significance of the money that can be empirically experienced, is not fully proven because the amount of salary is at the 12th position. Results from 2018 and 2020 differ slightly from those gathered in 2010, in terms of hierarchy of the motivational factors and their motivational potential. Noticeable was the decrease in importance of the "interesting job" factor (1/7), as well as the increase for the factor "salary amount" (8/4) and "independence"(9/2). The use of single-factor variance analysis (ANOVA), post hoc test and t-test showed statistically significant differences in the influence of motivational factors on the motivation across different subpopulations of respondents. The size of the impact of the motivational factors on motivation for work increases with the level of postgraduate training, and it is higher in those who are more satisfied with the salary, as well as for the officers in comparison to non-commissioned officers and civilian employees.