This paper describes the resource use and costs involved in supporting ventilator-dependent children and young people at home compared with those in hospital. Accommodation arrangements, patterns of service and resource use in the year prior to interview were recorded for 35 index cases aged 1-18 years using a piloted variant of the Client Services Receipt Inventory. Costs to the National Health Service (NHS), social services (excluding local authority housing costs), education (excluding basic statutory education costs), and voluntary and independent sectors were included. For each of the resources and supports used, a unit cost was calculated at 2002 prices, which was a close approximation to the long-run marginal opportunity cost. Of the 35 cases, 24 lived at home, seven were in hospital and four had transferred from hospital to home during the previous 12 months. Twelve used ventilation 24-h per day. The children and young people made intensive use of NHS services and resources. In total, the 35 cases cost just over pound 6.2 million to support during the year prior to interview; 92% of the costs were borne by the NHS. It was mostly, but not always, cheaper for children to live at home. A care package including qualified nurses and 24-h care (mean=pound 239,855 per year) was more expensive than a children's ward (mean=pound 155,158 per year), but less expensive than a long-term ventilation unit (mean=pound 301,888 per year) or an intensive care unit (mean=pound 630,388 per year), where most cases live whilst awaiting discharge. Support costs for children with complex ventilator dependency were seven times higher than those with simple ventilator dependency. These estimates provide commissioners and managers with good-quality data to inform the implementation of recently published national guidance on care for these children and young people.