  The alternative to the standard formulation of QPM in the infinite momentum
frame is suggested. The proposed approach does not require any extra
assumptions in addition, consistently takes into account the parton transversal
momenta and does not prefer any special reference system. The standard approach
is involved as a limiting case. In the result the modified relations between
the structure and distribution functions are obtained together with some
constraint on their shape. The comparison with experimental data offers a
speculation about values of effective masses of quarks, which emerge as a free
parameter in the approach.
