Separate compression samples of VT20 Ti-alloy Ti-5.9A1-2.1Zr-1.6V-1.4Mo (wt%), charged with 0, 0.15 and 0.36 wt%H, were deformed to true strain of 0.70 at a strain rates of 1×10-3 and 1×10-1 s-1 at test temperatures of 600 and 850 °C. H charging led to the varying microstructures ranging from equiaxed to lamellar ones depending on H level. In the course of deformation, their occurred refinement of microstructures with reduced interlamellar spacing depending on the test conditions. The contributions of these sources to microstructure evolution and flow properties were examined in an attempt to explore some correlation between them. An attempt is made to understand the effect of H present on the microstructure and flow properties to account for the variations in the parameters of the constitutive relationship.