A blade for a rotor of a wind turbine having a substantially horizontal rotor shaft, said rotor comprising a hub, from which the blade extends substantially in a radial direction when mounted to the hub, the blade having a longitudinal direction (r) with a tip end and a root end and a transverse direction, the blade further comprising: - a profiled contour (40, 42, 50) including a pressure side and a suction side, as well as a leading edge and a trailing edge with a chord having a chord length extending there between, the profiled contour, when being impacted by an incident airflow, generating a lift, wherein the profiled contour is divided into: - a root region having a substantially circular or elliptical profile closest to the hub, - an airfoil region having a lift-generating profile furthest away from the hub, and - a transition region between the root region and the airfoil region, the transition region having a profile gradually changing in the radial direction from the circular or elliptical profile of the root region to the lift-generating profile of the airfoil region, and wherein - the blade is provided with a flow guiding device added to the profiled contour (40, 42, 50) of the blade on the pressure side of the blade, the flow guiding device having an inflow surface with a start point attached to the profiled contour (40, 42, 50) and an end point located in a distance from the profiled contour (40, 42, 50) of the blade, the end point having a minimum distance ( d ep) to the profiled contour (40, 42, 50) of the blade, - the flow guiding device extending along at least a longitudinal part of the transition region and is arranged so as to generate a separation of airflow along at least a central longitudinal portion of the flow guiding device from the pressure side of the blade at a point between the flow guiding device and the trailing edge of the blade, when the blade is impacted by the incident airflow, wherein - the flow guiding device in at least the central longitudinal portion being arranged so that the end point has a relative chordal position, seen from the leading edge of the blade, lying in an interval between 40% and 92%, characterised in that - the inflow surface in at least the central longitudinal portion is formed so that, for each transverse cross-section, the minimum distance ( d ep) from the end point to the profiled contour is at least 15% of a maximum thickness of the profiled contour, and wherein the inflow surface is concave, and wherein the flow guiding device has a rear edge with a rear edge height, and wherein the rear edge height is substantially constant in at least the central longitudinal portion of the flow guiding device. - a profiled contour (40, 42, 50) including a pressure side and a suction side, as well as a leading edge and a trailing edge with a chord having a chord length extending there between, the profiled contour, when being impacted by an incident airflow, generating a lift, wherein the profiled contour is divided into: - a root region having a substantially circular or elliptical profile closest to the hub, - an airfoil region having a lift-generating profile furthest away from the hub, and - a transition region between the root region and the airfoil region, the transition region having a profile gradually changing in the radial direction from the circular or elliptical profile of the root region to the lift-generating profile of the airfoil region, and wherein - the blade is provided with a flow guiding device added to the profiled contour (40, 42, 50) of the blade on the pressure side of the blade, the flow guiding device having an inflow surface with a start point attached to the profiled contour (40, 42, 50) and an end point located in a distance from the profiled contour (40, 42, 50) of the blade, the end point having a minimum distance ( d ep) to the profiled contour (40, 42, 50) of the blade, - the flow guiding device extending along at least a longitudinal part of the transition region and is arranged so as to generate a separation of airflow along at least a central longitudinal portion of the flow guiding device from the pressure side of the blade at a point between the flow guiding device and the trailing edge of the blade, when the blade is impacted by the incident airflow, wherein - the flow guiding device in at least the central longitudinal portion being arranged so that the end point has a relative chordal position, seen from the leading edge of the blade, lying in an interval between 40% and 92%, characterised in that - the inflow surface in at least the central longitudinal portion is formed so that, for each transverse cross-section, the minimum distance ( d ep) from the end point to the profiled contour is at least 15% of a maximum thickness of the profiled contour, and wherein the inflow surface is concave, and wherein the flow guiding device has a rear edge with a rear edge height, and wherein the rear edge height is substantially constant in at least the central longitudinal portion of the flow guiding device.