  Structural analysis has been performed for a sample of 15 Southern early-type
disk galaxies, mainly S0s, using high resolution $K_s$-band images. The
galaxies are mostly barred and many of them show multiple structures including
bars and ovals, typical for S0s. The new images are of sufficient quality to
reveal new detail on the morphology of the galaxies. For example, we report a
hitherto undetected nuclear ring in NGC 1387, a nuclear bar in NGC 1326, and in
the residual image also a weak primary bar in NGC 1317. For the galaxies we (1)
measure the radial profiles of the orientation parameters derived from the
elliptical isophotes, (2) apply Fourier methods for calculating tangential
forces, and particularly, (3) apply structural decomposition methods. For
galaxies with multiple structures a 2-dimensional method is found to be
superior to a 1-dimensional method, but only if in addition to the bulge and
the disk, at least one other component is taken into account. {\it We find
strong evidence of pseudo-bulges in S0s}: ten of the galaxies have the shape
parameter of the bulge near to $n$ = 2, indicating that the bulges are more
disk-like than following the R$^{1/4}$-law. Also, six of the galaxies have
either nuclear rings, nuclear bars or nuclear disks. In all non-elliptical
galaxies in our sample the $B/T < $ 0.4, as typically found in galaxies having
pseudo-bulges. In two of the galaxies the $B/T$ flux ratio is as small as in
typical Sc-type spirals. This might be the hitherto undiscovered link in the
scenario in which spirals are transformedinto S0s. Also, bars in S0s are found
to be shorter and less massive, and have smaller bar torques than bars in
S0/a-type galaxies.
