Offshore helicopter transport represents a quite complex, socio-technical system. A number of factors affect the risk related to this activity, e.g. maintenance, design of helicopter/helideck, and the competence/training of the crew. The present paper presents an overall, holistic risk model, which aims at presenting the total risk picture and the risk influencing factors (RIFs) for helicopter transport. The main objective is to provide a tool for identifying the most effective risk reducing measures. The RIFs both for accident frequency and accident consequence are arranged hierarchically in a type of influence diagram, illustrating the effect of the various RIFs. Accident and incident statistics from North Sea helicopter transport are used in combination with expert judgements to assess the weight (importance) and the present status of the RIFs. The model is also used to provide numerical results.