The pathology, diagnosis and management of posterior plagiocephaly remains highly controversial. While the rationale for surgical management of true lambdoid synostosis is undisputed, opinions vary greatly on how to manage severe, unresolving, non-synostotic cases. We reviewed 39 cases of posterior plagiocephaly, 37 of which were treated conservatively. Of these, 34 patients had a significant improvement over the following year with sleep posture modification and/or physiotherapy. While only eight cases returned to complete normality, the remainder had deformities that were deemed mild by both mothers and surgeons, and did not merit surgery. Defining recalcitrant cases remains elusive as standard imaging is often unhelpful. While 3-D CT offers a much more accurate diagnosis of true lambdoid synostosis with bony union and allows objective assessment of the deformity, serial scans involve radiation doses that are difficult to justify. Clinical follow-up is the only reliable method at present.