Recently it has been claimed that infants with congenital muscular torticollis (CMT) are at risk of a delay in early motor milestones. The aim of the present study was to investigate whether infants with CMT are indeed at risk in comparison with a control group of healthy infants. A second aim was to investigate whether the time spent in a prone position and plagiocephaly had any influence on motor development. Eighty-two infants with CMT (35 females and 47 males) were compared with 40 healthy infants (18 females and 22 males). Motor development was assessed with the Alberta Infant Motor scale (AIMS). Multiple regression showed that infants in the CMT group had a significantly lower AIMS score than the control group at 2 months (p=0.03) and 6 months of age (p=0.05). Infants who spent at least three occasions daily in a prone position when awake had significantly higher AIMS scores than infants who spent less time prone at 2 months (p=0.001), 6 months (p<0.001), and 10 months of age (p<0.001). The CMT group achieved early motor milestones significantly later than the control group until the age of 10 months, but the risk of delay seems to be more strongly associated with little or no time prone when awake than with CMT.