A diet low in fermentable carbohydrates, oligosaccharides, disaccharides, monosaccharides and polyols (FODMAP) has been described as an effective nutritional approach in irritable bowel syndrome. There has been an increased demand for gluten- and lactose-free foodstuffs in the last few years, which are associated with gastrointestinal symptoms and are consumed by patients with gastrointestinal disease. This study aims to estimate the FODMAP content of industrial pre-packaged food products containing the ‘gluten-free’ and ‘lactose-free’ claims. The ingredient lists of the foodstuffs from a Portuguese food retail chain were verified and classified according to their estimated FODMAP content as ‘low’ and ‘high’, using as a reference the FODMAP cutoff values and the serving sizes established by the Monash University App. Descriptive statistics and the Pearson χ2 test were applied. From the 436 eligible products identified, most were classified as ‘low’ (53·0 %, n 231), 24·3 % (n 106) were classified as ‘high’ and 22·7 % (n 99) were classified as having ‘unknown’ FODMAP content. ‘High FODMAP’ products accounted for 12·2 % of those with ‘lactose-free’ claims and 31·6 % of those with ‘gluten-free’ claims. The ‘ready meals’ and ‘sauces, dressings, creams and soups’ were the food categories with the highest proportion of products with high FODMAP sources. This study showed that approximately a quarter of pre-packaged industrial foods targeted to gastrointestinal pathologies are high in FODMAP. The nutritional information on the label should be more specific, enabling more accurate dosing of FODMAP contents in foodstuffs and the establishment of the recommended serving sizes.