Positional plagiocephaly (deformational or occipital plagiocephaly) is the most common head-shape deformity, which is presented to specialist craniofacial units. The aim of management is to reduce pressure on the affected area in the expectation that brain growth will drive normalization of the head shape. Current management includes a variety of protocols based on repositioning advice or helmet orthotics. The aim of this study is to document changes in head shape associated with use of a passive orthotic mattress for the management of positional plagiocephaly of a series of 30 patients at Alder Hey Children’s Hospital between April 2008 and June 2010. Cranial vault asymmetry was assessed before treatment and was classified into mild, moderate, or severe plagiocephaly. Follow-up demonstrated a significant improvement in cranial vault asymmetry in those treated with the passive orthotic mattress.