Executive functions are part of a self-regulating mechanism that include various cognitive processes involved in purposeful, purpose-oriented and future-oriented behavior. It is consisted of four components: inhibition, work memory, cognitive flexibility and planning. The aim of the present study, which was part of longitudinal research, was to examine the relationship between parent assessments and objective measures of executive functions, whether the child's temperament, parental behavior and dimensions, and parental self-efficacy are the determinants of the executive functions of preschool children, and whether executive functions are related to behavioral problems in children. At this phase, the research involved 58 school-age children, attendants of kindergartens, and 54 parents of children, all from Rijeka. The children solved a several simple tasks of executive functions while parents evaluated the child's executive functions, behavioral problems, self-behaviors and self-efficacy in upbringing by means of questionnaires, while parental estimations of the child's temperament were used in the first phase of the research, which was conducted in 2014. Also, for the purpose of checking the metric characteristics of the Childhood Executive Functioning Inventory, the research has been extended to an online sample. In total 87 parents of children between the ages of 3 to 7 completed the online questionnaire. Their estimates with the estimates of 54 parents from the longitudinal survey were used to validate Inventory, which showed good metric characteristics. The research results show that executive function measures are negatively related to negative parental behavior, and only the age of the child and punitive discipline were important predictors in explaining executive functions of the child. This research has also shown that conscious control (as a temperament dimension) and deficit inhibition predicts the development of behavioral problems: internalized and outsourced. So, if the executive functions of a child are less developed, it is more likely that some form of behavioral problems will appear.