A method for adaptively controlling bandwidth of a carrier recovery loop in radio transmission systems, wherein the phase error in a PLL is adjusted to a minimum level by means of a loop filter incorporated in said PLL. The phase noise value in the local oscillator is determined and the value of the additive white gaussian noise in the PLL is estimated. Next these values are applied in a predetermined mathematical relationship indicative of the phase error in said PLL in such a manner that the desired wavelength of the PLL can be determined by corresponding to a minimum value of the phase error.