The invention seeks to provide a method and a system for identifying a dominant signal component in a biosignal including at least two signal components. A biosignal including a first signal component having a first frequency range and a second signal component having a second frequency range is obtained from a subject. First and second indicators are then determined, which characterize the probability distribution of a predefined property, such as frequency, of the biosignal on predetermined primary and auxiliary frequency bands, respectively. Based on the first and second indicators, the system detects which one of the first and second signal components is currently a dominant signal component in the biosignal. The knowledge of the dominant component may be utilized in different ways in different systems monitoring the state of the subject.