The coronavirus pandemic poses a great danger to the general population, and that is why it is important to achieve high enough vaccination rates against COVID-19 in order to develop herd immunity. In order to create the most effective vaccination program in Croatia, it is important to check whether the determinants of COVID-19 vaccination readiness obtained in foreign research are the same as those in Croatia. That is why the aim of the this research was to examine the differences in COVID-19 vaccination readiness with regard to different individual characteristics of people, to examine the contribution of different personality traits in the prediction of vaccination readiness, and to examine the representation of different reasons for vaccination or not to be vaccinated against COVID-19. The study involved 1,797 respondents (1369 female and 422 male respondents, also 6 declared themselves as others), whose ages ranged from 18 to 77 (M = 36.07; SD = 11.60). The obtained results suggest that the most common reasons for vaccination are the opinion that this will reduce the undesirable consequences of COVID, the desire to return to a normal lifestyle, and the opinion this protects their loved ones from a possible infection, while the most common reasons for not being vaccinated are the opinion that the vaccine is not sufficiently researched, side effects caused by the vaccine, and the opinion that the vaccine is not effective enough. The obtained data also indicates that males, people of younger age, people with lower education, people residing in smaller settlements, with lower income status, with a right-wing political orientation, people whose source of information is social media and the internet, who are not healthcare workers and people who have not recovered from COVID-19 show a lower COVID-19 vaccination readiness. Finally, it was shown that neuroticism and conscientiousness significantly contribute to the explanation of the variance of willingness to be vaccinated against COVID-19. More precisely, people with higher neuroticism and lower conscientiousness have a higher COVID-19 vaccination readiness.