The 43-item TNO-AZL Preschool Children Quality of Life (TAPQOL) questionnaire was developed to meet the need for a reliable and valid instrument for measuring parent's perceptions of health-related quality of life (HRQoL) in preschool children. HRQoL was defined as health status in 12 domains weighted by the impact of the health status problems on well-being. The aim of this study was to evaluate the psychometric performance of the TAPQOL. A sample of 121 parents of preterm children completed the TAPQOL questionnaire (response rate 88%) as well as 362 parents of children from the general population (response rate 60%). On the base of Cronbach's alpha, item-rest correlation, and principal component analysis, the TAPQOL scales were constructed from the data for the preterm children sample. The psychometric performance of these scales was evaluated for both the preterm children sample and the general population sample. Cronbach's alpha ranged from 0.66 to 0.88 for the preterm children sample and from 0.43 to 0.84 for the general population sample. The unidimensionality of the separate scales was confirmed by principal component analysis for both the preterm children sample and the general population sample. Spearman's correlation coefficients between scales were, on average, low. T-tests showed that the very preterm children, the children with chronic diseases, the less healthy and the less happy children had lower mean scores on the TAPQOL scales than healthy children, indicating a worse quality of life. This study shows that the TAPQOL is a reliable and valid parent's perception of HRQoL in preschool children. More research is needed to evaluate the psychometric performance of the TAPQOL in different clinical populations.