This study verified the influence of chronic mouth breathing on dentofacial growth and developmental in pre-school children. The study evaluated 73 children, both sexes, ranging from 3 to 6 years of age. After the otorhinolaryngological breathing diagnosis, 44 mouth-breathing children and 29 nasal-breathing children were compared according to facial and occlusal characteristics. The skeletal pattern measurements SN.GoGn, BaN.PtGn, PP.PM, Ar-Go, S-Go indicated a tendency to mouth-breathing children presenting a dolicofacial pattern. According to occlusal characteristics, only the intermolar distance showed a significant correlation with a narrow maxillary arch in mouth-breathing subjects. Based on the results of this study, mouth-breathing can influence craniofacial and occlusal development early in childhood.