Objective: The diagnosis of an incidental adnexal lesion during pregnancy has become more common after the widespread use of routine ultrasonography (US). The aim of this study was to examine the diagnostic approach, management strategy and the pathological findings in cases of adnexal lesions that were diagnosed and treated during pregnancy in our department. Materials and Methods: This was a 15-year retrospective study. Cases of adnexal lesions detected during routine prenatal care by US or while performing cesarean section, between January 1996 and December 2010 at Aretaieion Hospital of the National University of Athens, were analyzed. Results: In this study period 39 cases of adnexal lesions were diagnosed during pregnancy or cesarean section. The age of the women was between 21 and 40 years (mean age 32.4). Surgical excision of the lesions was decided in 32 cases and conservative treatment was followed in the remaining seven cases. Surgical removal of the lesions was performed during cesarean section in 13 cases of term gestations and in four cases of preterm gestations in which pregnancy termination was considered necessary. Laparotomy during the antepartum period led to excision of adnexal lesions in 15 cases. Histology revealed benign ovarian lesions in 25 cases (78.1%), borderline ovarian tumors in two cases (6.3%), malignant ovarian tumors in four cases (12.5%) and adenocarcinoma of the appendix in one case (3.1%) presenting as an ovarian mass. Discussion: The management of cases diagnosed with adnexal lesions during pregnancy remains controversial. According to the literature, the estimated risk of malignancy for adnexal masses during pregnancy is low (2-3%) and complications of these lesions are extremely rare. These data suggest that adnexal masses could be managed conservatively if possible with US follow-up. On the other hand, the results of this study showed a higher incidence of malignancy among adnexal lesions that were surgically treated (15.6%). Conclusion: Surgical intervention and histological examination in cases suspicious for malignancy at US and clinical findings remain the treatment of choice even during pregnancy.