  Pion valence distributions in nuclear medium and vacuum are studied in a
light-front constituent quark model. The in-medium input for studying the pion
properties is calculated by the quark-meson coupling model. We find that the
in-medium pion valence distribution, as well as the in-medium pion valence wave
function, are substantially modified at normal nuclear matter density, due to
the reduction in the pion decay constant.
