The renewables sector and particularly offshore wind energy is a fast developing industry over the last few years. Especially activities related to the Installation, Operation and Maintenance (O&M) of offshore wind turbines becomes a challenging task with inherent risks. This paper assesses the risks related to the above stages of a wind farm lifecycle using the FMECA (Failure Mode, Effects and Criticality Analysis) and HAZID (Hazard Identification) methods. All works, from installation to O&M are considered together with the wind turbine main components. An integrated risk analysis methodology is presented addressing personnel Safety (S), Environmental impact (E), Asset integrity (A) and Operation (O). The above is supplemented by a cost analysis with the aid of BBN (Bayesian Belief Networks) method in order to assist the decision making process related to installation and O&M tasks. All major risks and critical wind turbine components are identified as well as measures are suggested in order to prevent or mitigate them. Moreover, inspection and maintenance plans are elaborated in general for the mentioned activities.