  The pion decay constant f_pi plays a crucial role in many areas of low energy
particle physics. Its value may e.g. be deduced from experimental data on
leptonic pion decays. Here, we provide comments on several aspects of this
evaluation. In particular, we point out that at the present level of
experimental accuracy, the value of f_pi is sensitive to the value of the pion
mass chosen in its chiral expansion.
