Dentinoma is a rare odontogenic tumor showing the inductive effects of odontogenic epithelium on the connective tissue. A case of the tumor occurring in the region of the missing right mandibular second permanent premolar of an 11-year-old male is described. The tumor and the impacted right mandibular second deciduous molar were surgically removed. Histologically, areas of hyalinized collagen, osteodentin and tubular dentin were seen in a stroma varying from mesenchymal to more mature. Immunostaining for the distinct types I, III and IV collagens were negative in the hyalinized areas. Type IV collagen stained as a halo corresponding to the basal membrane zone surrounding the groups of odontogenic epithelial cells. Recovery was uneventful. There was no recurrence of the tumor during the first 10 months of follow-up.