UNLABELLED One of the most frequent congenital malformations is cleft lip and/or palate. The above-mentioned defect is a serious medical and social problem, and knowledge concerning its incidence pictures the scale of this phenomenon. THE AIM OF THE STUDY was to determine the prevalence of cleft lip and/or palate in children in Łódź during the period between 2001 and 2010. MATERIAL AND METHODS We were able to obtain data from The Polish Registry of Congenital Malformations concerning the number of live born infants, and birth of children with cleft malformations in Łódź during the period between 2001 and 2010. RESULTS The mean incidence of cleft malformations amounted to 1.16/1000 live born infants in Łódź during the period between 2001 and 2010. CONCLUSIONS During the period between 2001 and 2010, a significant decrease in the prevalence of cleft lip and/or palate was observed in Łódź. The most common type of defect was isolated cleft palate, while the most rare - cleft lip. Considering boys the most frequent defect was cleft lip and palate, while in girls - isolated cleft palate. Attention should be drawn to the fact of the decreased number of deliveries in Łódź, observed in the past decade.