Aim: The aim of this study was to provide basic representative data on the prevalence of malocclusions involving space deficiency in both primary and early mixed dentition and to examine the relationship between these malocclusions and orofacial dysfunctions. The results should be viewed from an orthodontic prevention and early treatment perspective. Subjects and methods: Orthodontic findings in the maxilla and mandible as well as the myofunctional status of 766 children in primary dentition and 2,209 children in mixed dentition were examined clinically in a cross-sectional study. The following parameters from each jaw were subjected to orthodontic analysis: crowding in the anterior and posterior regions of the maxilla and mandible in primary and mixed dentitions, deviations from normal maxillary arch forms in the primary dentition, deviations from normal anterior maxillary arch width in mixed dentition and maxillary apical base morphology in mixed dentition. Static and dynamic orofacial dysfunctions were documented with reference to specific parameters and clinical tests. Results: Crowding was observed in every tenth child in primary dentition (10.8%) and in every second child in mixed dentition (49.7%). Habitual open mouth posture, visceral swallowing, articulation disorders and oral habits were statistically significantly more frequent in children in primary dentition presenting a narrow maxillary arch. Reduced anterior maxillary arch width (compression) was statistically more frequent in children in early mixed dentitions with habitual open mouth posture. A narrow maxillary apical base correlated positively with all the orofacial dysfunctions analyzed. Conclusions: Deviations from a regular arch form become apparent very early during dentition development and coexist with specific orofacial dysfunctions. They are thus important indicators for the early detection of functional abnormalities, causing deviations from normal dentition development. In children with orofacial dysfunctions the development of a narrow maxillary dental arch should be prevented by myofunctional therapy and by educating the parents. Interceptive orthodontic measures to treat a narrow maxillary arch in primary and early mixed dentition should also focus on eliminating functional disturbing factors, such as orofacial dysfunctions. Interdisciplinary cooperation with specialists in other fields of medicine, e.g. otorhinolaryngology and speech therapy, is essential to achieve this goal.