Objective. The aim of this study was to examine the maxillary arch dimensions in cleft lip and/or palate infants in Northern Finland before surgery. Materials and methods. The subjects consisted of 70 Finnish cleft patients born between 1997–2004 in Northern Ostrobothnia Hospital District in Finland. The study casts were obtained before surgery at the mean age of 5.6 months (SD = 2.2). There were 42 children with cleft palate (CP) (26 girls/16 boys), 13 with unilateral cleft lip and palate (UCLP) (eight girls/five boys), eight children with cleft lip (CL)(two girls/six boys) and seven with bilateral cleft lip and palate (BCLP) (two girls/five boys). Conventionally-used landmarks were marked on study casts and cleft width, arch circumference, anterior and posterior arch width and arch length were measured with a digital sliding calliper. The statistical method was ANOVA. Results. The prevalence of CP in this study, 60% of all clefts, is higher than the average standards. There were statistically significant differences in cleft width, posterior and anterior arch width, arch length and arch circumference, when different cleft groups were compared. When differences between girls and boys were compared, boys had larger cleft size and arch dimensions generally, but the results were not statistically significant. Conclusions. The results show the large variation in the severity of cleft lip and/or palate deformity at birth and in maxillary arch dimensions between different cleft types. It also demonstrates the effect of phenotypic variability within the groups of cleft lip and/or palate.