In 2003, one in five Belgian infants underwent overnight polysomnography (PSG), representing a social security budget of €9.6 million. We performed a literature review of PSG and an analysis of Belgian social security data. To clarify why so many Belgian infants are tested, an exploratory qualitative study was carried out to understand the perceptions of the parents as well as the viewpoint of caregivers. The literature review clearly demonstrated that PSG cannot predict sudden infant death syndrome (SIDS). Cardiorespiratory events (CE) or desaturations are increased in pre- or dysmatures, but before the peak incidence of SIDS. Evidence on the relationship between CE and later psychomotor development was lacking, as well as on the number of apparent life threatening events that can be clarified by PSG. Belgian data revealed large differences between hospitals in PSG prescription. For 73% of PSG, no specific medical indication had been registered. Interviews with parents showed that PSG is still perceived as a screening test for SIDS. Once parents had tested their child, they also wanted the test for future siblings. It appeared that physicians often prescribe the test without informing parents clearly on its purpose. Interviews with representatives of Belgian caregiver organisations indicated that PSG is not promoted to evaluate SIDS risk. However, the word “SIDS-test” is commonly used. Belgian SIDS-prevention campaigns emphasize the importance of preventive measures but do not mention PSG. In Belgium, prescription of PSG for infants should decrease. Caregivers should give more explicit information to parents on the real value of PSG.