  It has been recently argued that low-luminosity gamma-ray bursts (LL-GRBs)
are likely a unique GRB population. Here, we present systematic analysis of the
lightcurve characteristics from X-ray to gamma-ray energy bands for the two
prototypical LL-GRBs 980425 and 060218. It is found that both the pulse width
($w$) and the ratio of the rising width to the decaying width ($r/d$) of theses
two bursts are energy-dependent over a broad energy band. There exists a
significant trend that the pulses tend to be narrower and more symmetry with
respect to the higher energy bands for the two events. Both the X-rays and the
gamma-rays follow the same $w - E$ and $r/d - E$ relations. These facts may
indicate that the X-ray emission tracks the gamma-ray emission and both are
likely to be originated from the same physical mechanism. Their light curves
show significant spectral lags. We calculate the three types of lags with the
pulse peaking time ($t_{peak}$), the pulse centroid time ($t_{cen}$), and the
cross-correlation function (CCF). The derived $t_{peak}$ and $t_{cen}$ are a
power-law function of energy. The lag calculated by CCF is strongly correlated
with that derived from $t_{peak}$. But the lag derived from $t_{cen}$ is less
correlated with that derived from $t_{peak}$ and CCF. The energy dependence of
the lags is shallower at higher energy bands. These characteristics are well
consistent with that observed in typical long-lag, wide-pulse GRBs, suggesting
that GRBs 980425 and 060218 may share the similar radiation physics with them.
