This invention relates to a positioning system for monitoring sensors or treatment devices which are to be accurately located on the skin of a patient, especially where professional assistance is unavailable, for example in a domestic environment. It comprises a positioning system for a patient monitoring sensor or treatment device with imaging means for detecting a texture or pattern on the skin of a patient to identify a sensor location, an image processing unit which is adapted to learn the required location of a sensor by storing the local texture or pattern, and means for guiding a user to reposition the sensor in the desired location by reference to the stored pattern.
