A sample of 40 bright spiral galaxies (BT < 12) with low inclination and without bar was observed with JHK filters. For this purpose the MAGIC NICMOS3 camera at the 2.2 m telescope of the Calar Alto observatory, Spain was used. With a newly developed 2-dimensional algorithm the distribution of the surface brightness was fitted simultaneously by corresponding functions for the disk- and bulge-structure. While the disk was fitted with an exponential function, the bulge profile was fitted with a generalized de Vaucouleurs Rbeta law, with the concentration parameter beta = 1/n as a further fit variable. The correlation of the resulting structural parameters of disks and bulges lead to some interesting relations: 1. The use of a variable exponent beta is necessary for a realistic description of the bulge structure; 2. Disks and bulges show similar correlations between effective radius, effective surface brightness and luminosity; 3. They populate a common strip in the fundamental plane; 4. From the correlations between beta and Hubble type some conclusions about the formation and evolution of spiral galaxies can be drawn.