Orientation imaging microscopy has been used to investigate the effects of Nb doping on the grain boundary plane distributions in TiO2 (rutile). By comparing the grain boundary plane distribution of the undoped material with theoretical estimates of grain boundary energy anisotropy of pure rutile, it is possible to show that the frequency of grain boundary planes is inversely correlated with grain boundary energy. In the case of Nb-doped material, this inverse correlation can also be demonstrated by a comparison of grain boundary plane frequency with measurements of surface energy anisotropy. In addition, by comparing the grain boundary plane distribution of doped and undoped materials with previous measurements of Nb grain boundary segregation in TiO2 as a function of grain boundary plane orientation, it is possible to explain the changes in grain boundary plane distribution which result from doping.