AimMost positional head deformities can be treated conservatively with postural correction training or a head orthosis (‘helmet’). We aimed to investigate whether infants with helmet therapy have cosmetic improvement in head deformity.MethodsA total of 376 infants at age 2–40 months who were diagnosed with mild–moderate–severe positional head deformity were enrolled. Among these infants, 101 infants were treated with helmet therapy or postural correction training. After matching by infant's age and time of therapy, three retrospective cohort studies of 56 infants were conducted for infants with plagiocephaly, brachycephaly and asymmetrical brachycephaly, respectively. The cephalic ratio (CR), radial symmetry index (RSI), cranial vault asymmetry (CVA) and cranial vault asymmetry index (CVAI) were compared between two groups before and after treatment.ResultsBefore treatment, no significant differences in CR, RSI, CVA and CVAI between groups were found. After treatment, compared with the postural correction training group, the helmet therapy group had significant improvements in CR, RSI, CVA or CVAI (Plagiocephaly: PCVA = 0.017, PCVAI = 0.028; Brachycephaly: PCR = 0.002; Asymmetrical brachycephaly: PRSI = 0.002, PCVA < 0.001, PCVAI < 0.001). Moreover, there was no significant difference in head circumference growth between the groups.ConclusionsHelmet therapy may be more effective in the treatment of mild–moderate–severe positional head deformity than postural correction training in infants. And helmet therapy may not hinder head circumference growth.