Since the advent of high brilliance synchrotron radiation sources, magnetic X-ray diffraction has become a standard microscopic probe for the investigation of magnetic structures, magnetic phase transitions and magnetic disorder phenomena. Modern experiments highlight the complementarity of this new probe to the standard neutron diffraction technique by taking advantage of the high momentum space resolution, the element sensitivity, the possibility to separate spin- and orbital contributions etc. In this paper we present selected experiments performed at HASYLAB which exemplify the present possibilities of resonant and non-resonant magnetic X-ray diffraction.