  We study generalized parton distributions in the impact parameter
representation, including the case of nonzero skewness xi. Using Lorentz
invariance, and expressing parton distributions in terms of impact parameter
dependent wave functions, we investigate in which way they simultaneously
describe longitudinal and transverse structure of a fast moving hadron. We
compare this information with the one in elastic form factors, in ordinary and
in k_T dependent parton distributions.
