  The band-width effect on interstellar reddening lines in the J-H vs. H-K_s
diagram of the 2MASS survey is investigated using synthetic color indices and
color excesses based on the Kurucz model atmospheres. At large interstellar
reddenings (E(H-K_s) larger than 1.0) reddening lines deviate considerably from
a straight line. The lines can be approximated by an equation: E(J-H) = r
E(H-K_s) + s E(H-K_s)^2, where the slope coefficient, r, and the curvature
coefficient, s, depend slightly on the intrinsic energy distribution of the
source. The curvature of the reddening lines is confirmed by the J-H vs. H-K_s
diagrams plotted by Straizys and Laugalys (2008) from 2MASS observations.
