Background: Atopic dermatitis is observed in up to 20% of children, hence the importance of tools to support its evaluation. Objective: To determine the validity and reliability of the Spanish adaptation of the IDQOL questionnaire in patients <4 years of age with atopic dermatitis (AD). Methods: Translation and back-translation of the questionnaire; a pilot test was done in 30 children with AD to arrive at a final version. Internal reliability (Cronbach's alpha) and correlation of IDQOL and SCORAD scores (Pearson correlation coefficient) were measured. Results: 102 children aged between two and 48 months were included. The Pearson correlation coefficient (r) of IDQOL and SCORAD scores was 0.697 (p = 0.0001), indicating a high positive correlation. The correlation between the severity measured by the caregiver and the SCORAD score (r = 0.565, p = 0.0001) proved to be low positive. The internal consistency of IDQOL using Cronbach's alpha was 0.84, indicating good consistency of the instrument for assessing quality of life. Conclusion:The IDQOL questionnaire in Spanish is a valid measure of quality of life in patients < 4 years with AD and is useful in monitoring and in clinical trials.