Professional development of preschool teachers is an important factor in promoting the quality of educational institutions. The process of professional development begins with formal education of preschool teachers, and continues throughout the working life of the 42 individual. The quality of the educational group depends on a number of factors, including professional development of preschool teachers, as persons engaged in early and preschool education activities and directly participating in the educational process. The aim of this research was to gain insight into the opinion of examinees on what they mean by the quality of educational institution and preschool teachers' professional development and their connection. Teachers included in the sample under the term quality of educational institutions include professional development, cooperation, open communication, compliance with SPS, respecting NCEPE, physical and material environment, motivation, evaluation and selfevaluation. Under the term professional development, preschool teachers mostly cited lifelong learning, reflection and self-reflection, professional training, mapping of professional development and self-evaluation. The results showed a statistically significant difference in the opinion of subjects with higher level of education on the impact of professional development of educators on the quality of educational institutions between teachers compared to lower level of education. There was also a statistically significant difference between preschool teachers with higher level of education in the frequency of participation in professional training compared to preschool teachers with lower level of education.