Apparatus (2) configured to assist a user in correctly positioning the apparatus on a drug delivery device (1), the apparatus comprising:attachment means for attaching the apparatus to the drug delivery device；an imaging arrangement for capturing at least one image of a portion of a delivery device；a processor for processing the captured at least one image to determine a position of the apparatus relative to the drug delivery device and to determine a manner in which the apparatus should be moved in order to correctly position the apparatus on the drug delivery device； anda display for displaying an indication of the manner in which the apparatus should be moved in order to correctly position the apparatus on the drug delivery device.
