The Co-Ni distribution in d-Al69.7(4)Co10.0(4)Ni20.3(4) was investigatedbased on X-ray and neutron diffraction data. The structure was modelledin higher dimensional space using the ‘charge-flipping’ and ‘low-densityelimination’ methods and it was quantitatively refined inthree-dimensional space employing a pseudo-approximant approach. Inhigher-dimensional description, the Co atoms are found at the centre ofone of the two symmetry independent occupation domains, enclosed byregions mainly occupied by Ni. The other occupation domain is mostlyoccupied by Al. In physical space Co atoms are located in the centres ofsmall Al pentagons and form pentagonal units, which are arranged indecagonal rings. On these sites Co is partly substituted by Ni, whileall other transition metal sites are occupied by Ni and to a minordegree by Al. The fraction of Co found on transition metal sitesdecreases with decreasing Co-Co distances, whereby Co is replaced by Ni.