  Rashba and linear Dresselhaus interactions are believed to yield dominant
contribution to the spin splitting of two-dimensional electrons in the quantum
wells based on A$_3$B$_5$ compounds. We show that the interfacial spin-orbit
interaction significantly renormalizes the value of the corresponding Rashba
($\alpha_{SIA}$) and Dresselhaus ($\alpha_{BIA}$) parameters. For this purpose,
we solve the effective mass equation in a quantum well supplemented by the
original boundary conditions on the atomically sharp interfaces and calculate
the interfacial contributions to $\alpha_{SIA}$ and $\alpha_{BIA}$. Our results
explain a considerable spread in the experimental data on spin-orbit parameters
in GaAs/AlGaAs quantum wells. We also demonstrated that the non-equivalence of
the interfaces leads to the anisotropy of the spin splitting even in quantum
wells with zero average electric field.
