The aim of the present study was to validate thirty-eight picture series of six pictures each developed within the PANCAKE (Pilot study forthe Assessment of Nutrient intake and food Consumption Among Kids in Europe) project for portion size estimation of foods consumed byinfants, toddlers and children for future pan-European and national dietary surveys. Identical validation sessions were conducted in threeEuropean countries. In each country, forty-five foods were evaluated; thirty-eight foods were the same as the depicted foods, and sevenfoods were different, but meant to be quantified by the use of one of the thirty-eight picture series. Each single picture within a pictureseries was evaluated six times by means of predefined portions. Therefore, thirty-six pre-weighed portions of each food were evaluatedby convenience samples of parents having children aged from 3 months to 10 years. The percentages of participants choosing the correctpicture, the picture adjacent to the correct picture or a distant picture were calculated, and the performance of individual pictures withinthe series was assessed. For twenty foods, the picture series performed acceptably (mean difference between the estimated portion numberand the served portion number less than 0·4 (SD ,1·1)). In addition, twelve foods were rated acceptable after adjustment for density differences.Some other series became acceptable after analyses at the country level. In conclusion, all picture series were acceptable forinclusion in the PANCAKE picture book. However, the picture series of baby food, salads and cakes either can only be used for foodsthat are very similar to those depicted or need to be substituted by another quantification tool.