Plagiocephaly is a generic term which enlarges phenotype characteristics of cranial asymmetry, having in common cranial obliquity. It can be due to lambdoid synostosis, unilateral coronal suture or deformational (positional, without synostosis, on healthy cranial sutures). Although rare, plagiocephaly had a sensible increase in diagnosis in coincidence with the campaign to avoid child sudden death in the USA (“Back to sleep, in 1992). The campaign reached its goal, with the orientation to sleep in dorsal decubitus, in avoiding children's sudden death. However, at the same time, the plagiocephaly diagnosis rate reached the highest grades ever seen. That time studies may have suffered this circumstantial influence, with possible misdiagnosis involving deformational plagiocephaly, and the synostosis correlate one. Our hypothesis is that maybe it can be true and safe to perform differential diagnosis between those conditions which determine oblique cranial asymmetry, on clinical and physical examination. We revised the literature searching for reliable methods to achieve safe correct diagnosis and treatment of each condition. We found many studies showing great variability in findings on physical examination. There is many signals that can orientate the diagnosis, however in some cases it is a challenge to consider reliable diagnosis only on physical examination.