To develop an index that assesses the degree of adherence to existing diet-lifestyle recommendations for preschoolers (Preschoolers Diet-Lifestyle Index (PDL-Index)) and to investigate its association with obesity.The PDL-Index was constructed using eleven components (i.e. questions regarding the frequency of consumption of selected foods/food groups, time spent on television watching and on moderate-to-vigorous physical activities).Scores from 0 to 4 were assigned to all components of the index. The PDL-Index total score ranged from 0 to 44. Higher values of the PDL-Index indicate greater adherence to dietary and lifestyle recommendations for preschoolers or otherwise greater adherence to healthier dietary-lifestyle patterns.As a validation procedure, a sample of 2287 preschoolers from Greece (GENESIS study) was used.The participants following healthier diet-lifestyle patterns (third tertile of PDL-Index) were less likely to be obese or overweight/obese compared to those following unhealthy diet-lifestyle patterns (first tertile of PDL-Index). It was observed that a 1/44 unit increase in the score of the PDL-Index was associated with approximately 5 % and 3 % lower odds of being obese and overweight/obese, respectively. Statistically significant results were observed after adjusting for potential confounders.The suggested PDL-Index could help public health policy makers in identifying vulnerable population subgroups and developing cost-effective, targeted intervention actions both in family and preschool settings. In addition, health-care professionals can use the PDL-Index to evaluate diet quality, lifestyle and risk for overweight/obesity at an individual level and counsel parents accordingly.