  In the framework of the instanton vacuum model we evaluate the Chiral
Perturbation Theory (ChPT) low-energy constants h_3,l_7. We found that in the
instanton vacuum model the constant l_7 is very sensitive to the shape of the
instanton and the instanton vacuum parameters. We evaluated the constant l_7
for two different zero-mode profiles and as a function of the average instanton
size \rho and inter-instanton distance R. Our result agrees with an old "order
of magnitude" estimate of this constant from [1]. The obtained value of l_7
implies that the pure QCD contribution to the pion mass difference is small,
~1% of the observed experimental value.
