The evaluation of the upper airway (UA) includes the physical examination of pharyngeal structures and a number of imaging techniques that vary from the mostly used lateral cephalometry and computed tomography to more sophisticated methods such as tri-dimensional magnetic resonance image (MRI). Other complex techniques addressing UA collapsibility assessed by measurement of pharyngeal critical pressure and negative expiratory pressure however are not routinely performed. These methods provide information about anatomic abnormalities and the level of pharyngeal narrowing or collapse while the patient is awake or asleep. Data suggest that individual patients have different patterns of UA narrowing. So, the best method for evaluating obstruction during obstructive events remains controversial. In general, in clinical practice physical examination including a systematic evaluation of facial morphology, mouth, nasal cavity and the pharynx as well as simple imaging techniques such as nasopharyngoscopy and cephalometry have been more routinely utilized. Findings associated with obstructive sleep apnoea (OSA) are UA narrowing by the lateral pharyngeal walls and enlargements of tonsils, uvula and tongue. Additionally cephalometry identifies the most significant craniofacial characteristics associated with this disease. MRI studies demonstrated that lateral narrowing of UA in OSA is due to parapharyngeal muscle hypertrophy and/or enlargement of non adipose soft tissues. The upper airway evaluation has indubitably contributed to understand the pathophysiology and the diagnosis of OSA and snoring. Additionally, it also helps to identify the subjects with increased OSA risk as well as to select the more appropriate modality of treatment, especially for surgical procedures.