Abstract: The invention relates to a method for separating plastic particles (P) from a suspension (L), e.g. from a cellulose mass or cellulose pulp suspension, in which the fiber-floc material is broken for loosening the plastic particles (P). In the method, turbulent flows are caused to said suspension (L), by means of which flows the particles (P) to be separated are separated from the remaining mass as the fiber network is decomposing, whereby lighter particles (P) are separated. In the method, the suspension (L) obtained in the previous phase is subjected to such a treatment that a concentration difference is achieved, which prevents the fiber network from reforming and thereby the plastic particles (P) from binding thereto, and a flow (F) is directed to the separation point, where the plastic particles (P) are separated from the suspension (L).