Abstract Aim To evaluate the effect of the cervical headgear on the development of obstructive sleep apnoea and subsequent alterations of oropharyngeal dimensions. Materials and method An electronic database search of published and unpublished literature was performed (MEDLINE, Cochrane Central Register of Controlled Trials, Cochrane Database of Systematic Reviews, Clinical Trials.gov and National Research Register). Search terms included obstructive sleep apnoea, sleep disorders, pharyngeal dimensions and headgear. A risk of bias assessment was conducted using the ACROBAT-NRSI tool for non-randomised studies. Results Of the 51 articles initially retrieved, only three were eligible for inclusion, while the remainder were retrospective cohort studies presenting serious risk of bias primarily due to undetected confounding factors or selection bias. No quantitative synthesis was possible. One study assessed the potential effect of isolated headgear treatment on apnoeic indices, while two studies described pharyngeal airway dimensions after the use of headgear alone or in combination with an activator appliance. Overall, increased apnoeic indices and the oxygen desaturation index were detected for headgear users. Dimensional changes in the posterior airway space were comparable after headgear or activator use, while combined headgear-activator treatment led to an increase in posterior pharyngeal area when compared with isolated fixed appliance therapy. Conclusions Due to methodological inconsistencies and apparent risk of bias of the existing studies, no robust conclusions can be drawn. Prospective controlled or randomised controlled trials are deemed necessary to provide evidence on the effect of headgear treatment on sleep apnoea or pharyngeal airway dimensions.