Childhood obesity is an issue of public health concern globally. This review reports on levels of overweight and obesity in Irish children and examines some aspects of their diet and lifestyle proposed to promote or protect against increasing body fatness in children. While there is still some debate with regard to the most appropriate cut-off points to use when assessing body fatness in children, approximately one in five Irish children (aged 2–17 years) have been classified as overweight (including obese) according to two generally accepted approaches. Furthermore, comparison with previous data has shown an increase in mean body weight and BMI over time. On examining dietary patterns for Irish children, there was a noticeable transition from a less energy dense diet in pre-school children to a more energy dense diet in older children and teenagers, associated with a change to less favourable dietary intakes for fibre, fat, fruit and vegetables, confectionery and snacks and sugar-sweetened beverages as children got older. A significant proportion of school-aged children and teenagers reported watching more than 2 h television per day (35 % on school-days and 65 % on week-ends) compared with 13 % of pre-school children. For children aged 5–12 years, eating out of the home contributed just 9 % of energy intake but food eaten from outside the home was shown to contribute a higher proportion of energy from fat and to be less fibre-dense than food prepared at home. Improvements in dietary lifestyle are needed to control increasing levels of overweight and obesity in children in Ireland.