The aim of this study was to evaluate the prevalence and pattern of agenesis, supernumerary teeth, impacted teeth and transpositions, as well as the relation between them, in a Portuguese sample.The study sample consisted of 2888 patients, observed between 2005 and 2009 at the Dentistry Clinic of the Instituto Superior de Ciências da Saúde-Norte (ISCSN, Portugal). The study included evaluation of the following parameters: agenesis of all teeth, supernumerary teeth, impacted permanent teeth and tooth transposition. The age range varied from 7 to 21 years. In order to study the absence of the third molar, subjects aged below 14 years were excluded. Statistical analysis was performed using SPSS(®).Excluding third molars, the prevalence of tooth agenesis, supernumerary teeth, impacted teeth and transpositions was 6.1%, 0.8%, 1.8% and 0.2%, respectively, for this Portuguese population. There was a significantly higher prevalence of supernumerary teeth in males than in females (P < 0.05). The mesiodens was the most frequent supernumerary tooth, the upper canine was the most frequent impacted tooth, and the upper canine and upper lateral were the two most frequently transposed teeth. There was a significantly higher prevalence of missing third molars in the impacted canine group than in the non-impacted canine group (P < 0.05).Agenesis is the most frequent dental anomaly. There are no differences between genders, except for supernumerary teeth, which are found more frequently in men. A relation between third molar agenesis and impacted canines was found.