[en] The estimation of the phase equilibrium line in the hafnium phase diagram has been made on the basis of analyzing the data on the similarity of the physical and chemical properties of titanium, zirconium and hafnium. To determine the T-p diagrams for hafnium, the coordinates of the ternary points of α-β-ω-equilibrium of titanium and zirconium have been used and their T-p diagrams have been considered. From the intersection of the α-β-equilibrium line of hafnium and the line connecting the ternary points of zirconium and titanium the approximate coordinates for the ternary point of α-β-ω-equilibrium of hafnium have been determined. The pressure estimation has been made of the α-ω-equilibrium of hafnium at room temperature. It is supposed, that the pressure of α→ω transformation of hafnium should exceed the pressure of the α-ω-equilibrium and could be experimentally observed at pressures of approximately 300 to 350 kbar and higher. It is evident, that the phase transformations in hafnium, discovered under shock waves at a pressure of approximately 400 kbar, are related not to the electronic α→β transitions, but to the α→ω transformation similar to the α→ω transformation in zirconium and titanium under shock waves