We previously described the development and validation of the 'Simple Measure of the Impact of Lupus Erythematosus in Youngsters' (SMILEY) for the reliable assessment of health-related quality of life (HRQOL) in children with systemic lupus erythematosus (SLE). The objectives of this new study were to determine the relationship of SMILEY scores to patient's/parent's assessment of HRQOL and SLE status, and physician's assessment of disease activity and damage over time. In this multicentre study, 68 children with SLE and parents completed SMILEY including the global HRQOL and SLE status assessments, physicians completed disease activity and damage tools at two time-points. Spearman rho was calculated between SMILEY scores and other scales, and between interval changes in SMILEY scores and other scales. SMILEY scores correlated with patient/parent assessments of global HRQOL and SLE status, disease activity and damage, confirming previous findings. The change in disease activity and damage measures correlated most strongly with the changes in SMILEY domains, Limitation and Burden of SLE. Results provide preliminary evidence that Limitation and Burden of SLE domains of SMILEY reflect the impact of disease activity and damage on HRQOL.