Wind turbine blade (10) including adjustable lift-regulating means (12, 13, 15, 17, 19, 21) arranged on or at the surface of the wind turbine blade (10), said lift-regulating means being provided with activating means by means of which they can be adjusted and thus alter the aerodynamic properties of the blade (10). The lift-regulating means (12, 13, 15, 17, 19, 21) and the activating means are adapted and arranged such that by activation of the activating means, the lift can be reduced in a zone extending in the longitudinal direction of the blade (10) from a first position adjacent the blade tip (14) to a second position between the first position and the blade root (16) and this second position is variable in the longitudinal direction of the blade (10) by adjusting the activate means. The lift-regulating means are formed of at least one flexible flap (12, 13, 15, 17, 19, 21). The invention further relates to a wind turbine rotor including such wind turbine blades, to a wind turbine and to a method of controlling the wind turbine.