The image placement is and remains an important aspect of photomask metrology. Not only the position accuracy of features for an individual mask - representing one layer in a complete chip design have to meet stringent requirements, the complete mask set for all layers have to match in order to get a functional device. At a time were registration and overlay errors were counted in micrometer it was enough to compare one mask with another by a so called overlay machine. This approach works sufficiently until placement specification reached the "nanometre range" and the development of dedicated 2D coordinate measurement systems became necessary. Since then, pattern placement metrology tools became "enabler" for the continuous improvement of pattern placement accuracy on photomask and the improvement of the final wafer overlay error. This paper reviews and discuss current trends of pattern placement metrology on photomasks, highlighting the major error drivers and will focus on current and future requirements for in - die registration.© (2011) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.