An arrangement for lowering and raising service tools used for offshore wind turbine blade and tower maintenance, comprising: a truss system, a rigging and a rigging pulling in and letting out means, wherein the truss system, comprising booms, pivotally attached to a supporting means, which are adapted to be leaned against or releasably fixed to a wind turbine tower or wind turbine tower mooring elements; wherein the rigging and a rigging pulling in and letting out means are operably connected with the truss system, so to allow lowering and raising service tools used for offshore wind turbine blade and tower maintenance, wherein - the truss system, comprising two booms, the booms having two ends: a forward end and a rear end, wherein the forward ends of the booms are pivotally attached to a supporting means, which are adapted to be leaned against or releasably fixed to a wind turbine tower or wind turbine tower mooring elements; - the rigging comprising a carrying rope, the service tool lowering and raising arrangement's three positioning ropes and booms' hanging ropes, - the rigging pulling in and letting out means comprising: three positioning rope's winches, two of which are mounted at the rear ends of the booms and one positioning rope's winch, adapted to be releasably fixed to a wind turbine generator platform; a hanging ropes' winches, mounted on, or adapted to be releasably fixed to a wind turbine generator platform; and a carrying rope's winch, mounted on, or adapted to be releasably fixed to a wind turbine generator nacelle; wherein end one of the carrying rope is adapted to be operably connected to the carrying rope's winch; end two of the carrying rope is adapted to be connected to the service tools used for wind turbine blade and tower maintenance; ends one of the positioning ropes are adapted to be connected to the side or lower part of the service tools; ends two of the two positioning ropes are adapted to be operably connected to respective positioning rope's winch and; ends one of the booms' hanging ropes are adapted to be operably connected to the hanging ropes' winches, ends two of the booms' hanging ropes are adapted to be connected to the forward ends and the rear ends of the booms. - the truss system, comprising two booms, the booms having two ends: a forward end and a rear end, wherein the forward ends of the booms are pivotally attached to a supporting means, which are adapted to be leaned against or releasably fixed to a wind turbine tower or wind turbine tower mooring elements; - the rigging comprising a carrying rope, the service tool lowering and raising arrangement's three positioning ropes and booms' hanging ropes, - the rigging pulling in and letting out means comprising: three positioning rope's winches, two of which are mounted at the rear ends of the booms and one positioning rope's winch, adapted to be releasably fixed to a wind turbine generator platform; a hanging ropes' winches, mounted on, or adapted to be releasably fixed to a wind turbine generator platform; and a carrying rope's winch, mounted on, or adapted to be releasably fixed to a wind turbine generator nacelle; wherein end one of the carrying rope is adapted to be operably connected to the carrying rope's winch; end two of the carrying rope is adapted to be connected to the service tools used for wind turbine blade and tower maintenance; ends one of the positioning ropes are adapted to be connected to the side or lower part of the service tools; ends two of the two positioning ropes are adapted to be operably connected to respective positioning rope's winch and; ends one of the booms' hanging ropes are adapted to be operably connected to the hanging ropes' winches, ends two of the booms' hanging ropes are adapted to be connected to the forward ends and the rear ends of the booms. three positioning rope's winches, two of which are mounted at the rear ends of the booms and one positioning rope's winch, adapted to be releasably fixed to a wind turbine generator platform; a hanging ropes' winches, mounted on, or adapted to be releasably fixed to a wind turbine generator platform; and a carrying rope's winch, mounted on, or adapted to be releasably fixed to a wind turbine generator nacelle; wherein end one of the carrying rope is adapted to be operably connected to the carrying rope's winch; end two of the carrying rope is adapted to be connected to the service tools used for wind turbine blade and tower maintenance; ends one of the positioning ropes are adapted to be connected to the side or lower part of the service tools; ends two of the two positioning ropes are adapted to be operably connected to respective positioning rope's winch and; ends one of the booms' hanging ropes are adapted to be operably connected to the hanging ropes' winches, ends two of the booms' hanging ropes are adapted to be connected to the forward ends and the rear ends of the booms.