This chapter reviews the psychometric properties, validation, and strengths and weaknesses of the most common measurement tools used for the subjective evaluation of sleepiness. Subjective measures of sleepiness described in the chapter include visual analogue scales (VAS), Stanford sleepiness scale (SSS), Karolinska sleepiness scale (KSS), Epworth sleepiness scale (ESS) pediatric sleep questionnaire, sleepiness subscale (PSQ-SS) and pediatric daytime sleepiness scale (PDSS). Children present with a variety of sleep disorders associated with excessive sleepiness. Subjective sleepiness is critical as it is often the initial symptom of underlying sleep pathology, and a major presenting complaint that clinicians must understand and address. More work is needed on potential cultural and racial differences in subjective sleepiness and in relation to specific types of measurement. It has been shown that subjective sleepiness is accompanied by EEG changes including selective slowing of specific frequency bands.