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 position and the blade root (16) and this second position is variable in the longitudinal direction of the blade (10) by adjusting 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.