  We present a calculation of cut-off effects at tree-level of perturbation
theory for the K and D mesons using the twisted mass formulation of lattice
QCD. The analytical calculations are performed in the time-momentum frame. The
relative sizes of cut-off effects are compared for the pion, the kaon and the D
meson masses. In addition, different realizations of maximal twist condition
are considered and the corresponding cut-off effects are analyzed.
