  We compute the one-loop corrections to the triple Higgs self-interaction
$hhh$ in the framework of the Standard Model (SM), the Two Higgs Doublet Model
type III (THDM-III) and the Littlest Higgs Model with T parity (LHBM+T). Our
results are compared with previous results for the SM. In particular, we find
that an imaginary part for the $\lambda_{hhh}$ form factor is induced when one
of the Higgs boson legs is off-mass shell with 4-momentum magnitude higher than
the Higgs boson mass. This contribution is sensitive to virtual effects of the
Higgs self-interaction, that induces a radiative correction to the $hhh$
coupling of order 11%. However, the radiative corrections associated to the new
degrees of freedom of the THDM-III and the LHBM+T are rather smaller and
comparable to the $W^\pm$ and $Z^0$ gauge bosons one-loop corrections.
