The invention relates to a method and a device for determining the time curve of the depth of breath (T) of a person, in particular a sleeping person. Height profiles (H) of the person (1) at individual recording time points are continuously determined. Height profiles from adjacent recording time points are combined to give segments. The region which indicates the abdomen or chest region of the person depending on a corresponding reference point or reference region (21) is selected as an observation region (22). For each height profile (H) within the segment (S1,..., Sq), the corresponding average value of the distances of the points of the height profile (H), which points lie within the observation region (22), from a reference point or reference object is separately determined. For the segment (S1,..., Sq), a signal (si) is determined and for each recording time point (t1,..., tp) of the height profile (H), the average value determined for this height profile (H) is associated with said signal. On the basis of the determined signal (si), in particular on the basis of the amplitude of said signal, one or more values which characterise the time curve of the depth of breath (T) are determined.
