  We present a detailed study of the structural properties of four
gravitationally lensed disk galaxies at z=1. Modelling the rotation curves on
sub-kpc scales we derive the values for the disk mass, the reference dark
matter density and core radius, and the angular momentum per unit mass. The
derived models suggest that the rotation curve profile and amplitude are best
fit with a dark matter component similar to those of local spiral galaxies. The
stellar component also has a similar length scale, but with substantially
smaller masses than similarly luminous disk galaxies in the local universe.
Comparing the average dark matter density inside the optical radius we find
that the disk galaxies at z=1 have larger densities (by up to a factor of 7)
than similar disk galaxies in the local Universe. Furthermore, the angular
momentum per unit mass versus reference velocity is well matched to the local
relation, suggesting that the angular momentum of the disk remains constant
between high redshifts and the present day. Though statistically limited, these
observations point towards a spirals' formation scenario in which stellar disks
are slowly grown by the accretion of angular momentum conserving material.
