The effect of cross-link density on the structure of Poly-(N-isopropylacrylamide) microgel particles prepared by emulsion polymerization was investigated by static and dynamic light scattering measurements. According to these measurements the gel particles cannot be considered as homogeneous spheres. The structure of the gel particles strongly depends on the degree of cross-linking. At high cross-link density the particles can be described with a Gaussian segment density distribution. With decreasing cross-link density the structure of the microgel particles tends toward that of a highly branched coil.