A dentigerous cyst of the impacted mandibular premolar in two children was radio graphically diagnosed. The treatment modality of marsupialization or enucleation combineb with orthodontic means was chosed according to the cyst position, cyst size, level of root formation, and the degree of tilted tooth axis. Following extraction of mandibular primary molars and surgerical management, the developing succedaneous premolar erupted naturally. Proper diagnosis and early surgical intervention to the teeth involved would have a better prognosis for children than adult. Children have a greater capacity to regenerate bony structure and the teeth with open apices have a great eruptive potential. Marsupialization is a good way to conserve a impacted tooth affected by a dentigerous cyst and to permit its eruption.