X-Ray diffraction (XRD) analysis was used to study the influence of alloying with 5 at.% Nb, 5 at.% Zr and 5 at.% (Zr+Hf) on the lattice parameters of the γ(TiAl) and α2(Ti3Al) phase in the intermetallic alloys based on Ti-44Al-0.2B (at.%). Before XRD analysis duplex structures with near the same microstructural parameters were obtained in samples of the alloys. The XRD data were used to calculate the tetragonal distortion (cγ / aγ ratio) of the γ phase, the cα2 / aα2 ratio of the α2 phase and the γ / α2 lattice misfits of the alloys. The highest tetragonal distortion (cγ / aγ) of the γ unit cell (cγ / aγ =1.0124) is observed for the base Ti-44Al-0.2B alloy, followed by the Nb-, (Zr+Hf)- and Zr-containing alloy (cγ / aγ =1.0116, 1.0075 and 1.0069, respectively). The cα2 / γα2 ratio is insignificantly changed depending on alloying. Doping with Zr and Zr+Hf leads to a noticeable decrease in the γ / α2 lattice misfits as compared with the alloy doped with Nb and the base alloy. For instance the γ / α2 lattice misfits determined in both crystallographic directions of the γ phase in the Ti-44Al-5Zr-0.2B and Ti-44Al-5Nb-0.2B alloys were found to be ε110 / ε101= 0.93 / 0.59 and ε110 / ε101=1.38 / 0.79, respectively. It has been recently revealed that γ-TiAl alloys with near the same duplex structures based on Ti-44Al-0.2B and doped with Zr and Zr+Hf demonstrated appreciably higher creep resistance than the alloy doped with Nb and the base alloy. It is assumed that the lower cγ / aγ ratios obtained for the Zr- and (Zr+Hf)-containing alloys contribute to the reduction of creep resistance. The fact that the Zr- and (Zr+Hf)-containing alloys showed higher creep resistance than the Nb-containing alloy should be mostly attributed to the lower γ / α2 lattice misfits in the Zr- and (Zr+Hf)-containing alloys and the higher solution hardening caused by doping with Zr and Hf. Therefore, the impact of alloying on the creep and heat resistance in β-solidifying γ-TiAl alloys should be considered taking into account the changes of the lattice parameters of the γ(TiAl) and α2(Ti3Al) phase, which influence the physical processes determining the creep behavior.