Adenoid hypertrophy is the most common cause of nasal obstruction in paediatric patients. Over the years, various methods to assess the adenoid size were proposed such as the posterior rhinoscopy and the radiological examination of the nasopharynx. Nasal endoscopy was introduced for children in the 80's, and nowadays this is a known and diffuse method in routine practice. The purpose of this article is to describe the personal experience in the assessment of the adenoid size in children, with a particular regard to the flexible nasal endoscopy, and to analyse the literature reports. The personal technique is described in performing nasal endoscopy in paediatric patients, reporting advantages and possible disadvantages of the procedure. A retrospective analysis was conducted on 6036 children since 1999 to 2010. In most cases children fully collaborated to complete the exam. No major or minor complications (such as nose bleedings or other traumatic injuries) were observed. No topical intranasal decongestant, local or general anaesthesia were used in our series. In our opinion, nasal endoscopy in children is a reliable, safe, accurate, easily tolerated and dynamic diagnostic method to assess the adenoid size.