PurposeAvailability and access to food is a determinant of obesity. The aim of this study was to examine food availability within and outside of post-primary schools in Ireland.Design/methodology/approachData on the internal school food environment were collected from 63 post-primary schools using questionnaires. The external school food environment for these 63 schools was assessed by mapping food businesses within 1 kilometre of schools, using a Geographic Information System (GIS). Food businesses were categorised based on type of food sold.FindingsA total of 68.3% of schools had a canteen, 52.5% had a small food shop and 37.1% had a vending machine. A total of 32.7% of schools reported selling chips (French fries) in their canteen while 44.2% of schools reported selling energy-dense nutrient-poor foods in their school shop. Of the schools surveyed, there was an average of 3.89 coffee shops and sandwich bars, 3.65 full service restaurants, 2.60 Asian and other ‘ethnic’ restaurants, 4.03 fast food restaurants, 1.95 supermarkets, 6.71 local shops and 0.73 fruit and vegetable retailers within a 1km radius of the post-primary schools. Findings are presented by geography (urban/rural), disadvantage (DEIS/non DEIS), gender (girls/boys/mixed) and food policy in place at the school (yes/no).Practical implicationsThese data will facilitate schools working on the framework for Health Promoting Schools in Ireland.Originality/valueThe study explores the internal and external school food environment. GIS have been used to link the external food environment to specific schools thus allowing a comprehensive analysis of the schools' food environment. To our knowledge, this is the first time that both environments are explored simultaneously.