Tooth impaction is defined as any tooth that fails to erupt into a normal functional position and remains unerupted in the jaw beyond the time of its normal eruption. Primary impaction of primary teeth is rare. Furthermore, a combination of eruption failure of primary second molars and horizontally impacted permanent first molars has not yet been reported. The purpose of this study was to present the treatment of two cases of primary impaction of primary second molars combined with horizontally impacted permanent first molars. The impacted primary second molars were extracted, and orthodontic traction was performed to induce normal eruption of the permanent first molars. We then regained space for the eruption of the second premolar and applied a space maintainer to secure the space and induce successful eruption of succedaneous teeth and normal function of permanent first molars in their positions.