  The decay constant of the $\eta$-meson in the framework of 'resummed' chiral
perturbation theory is discussed. A theoretical prediction is compared to the
available determinations. Compatibility of these determinations with the latest
fits of the SU(3) low energy coupling constants is investigated. Preliminary
results for the obtained constraints on the low energy coupling constants
$L^r_5$ and $L^r_4$, using Bayesian statistical approach, are presented.
