A method and a device determine a time curve of the depth of breath of a sleeping person. Height profiles of the person 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 is selected as an observation region. For each height profile within the segment, the corresponding average value of the distances of the points of the height profile, which points lie within the observation region, from a reference point is determined. For the segment, a signal is determined and for each recording time point, the average value determined for this height profile is associated with the signal. On the basis of the determined signal, values which characterize the time curve of the depth of breath are determined.
