The relationship between television (TV) viewing and overweight in children is likely to be influenced by the quality of measures used. We systematically reviewed studies related to overweight in children that had included a measure of TV exposure. Literature searches were conducted in MedLINE, PsychInfo, SportDiscus and ISIWeb of Science. Methods of assessing TV viewing were evaluated, including the type of measure, the administration procedure and reported psychometric properties. The majority of studies assessed TV viewing using self-report surveys and very few studies used direct observation. The validity or reliability of measures was often not examined. The majority of tools that were evaluated were compared with another self-report measure or an objective measure of physical activity. TV viewing measures should be selected that are specific to the research question, the study design, as well as methodological feasibility. However, it is recommended that measures of TV viewing be used only if they have psychometric data to support their validity and reliability. Selecting measures that are valid and reliable enables us to examine with greater accuracy the influence of TV viewing on childhood overweight, as well as the efficacy of interventions designed to reduce TV viewing in children.