We developed an isogeometric shell element based on the Kirchhoff-Love shell theory [Kiendl et al. 2009]. This element formulation requires that the basis functions are at least C¹-continuous across the elements, which does not represent a general problem for NURBS. Due to the higher order basis functions it is locking-free and no rotational degrees of freedom are used. Moreover, the isoparametric description is very advantageous in large deformation (geometrically nonlinear) structural analysis. A CAD surface model can be used for the analysis without further modification. In shape optimization the three models for design, analysis and shape optimization are merged into one model and no transformation from a FE mesh back to a CAD geometry is necessary.