Static light scattering, dynamic light scattering, and small-angle X-ray scattering are powerful tools to analyze structures of various polymer assemblies formed in solution. In this article, we briefly explain those experimental techniques along with their historical background, and review their applications to the following polymer solution systems: (1) associating homopolymer solutions, (2) aqueous solutions of the polyanion–polycation mixture forming polyion complex colloids, (3) block copolymer solutions forming polymer micelles of various morphologies, (4) aqueous solutions of amphiphilic random and alternating copolymers forming the flower micelle or flower necklace, and (5) aqueous solutions of the globular protein–surfactant mixture. Different scattering techniques are combined with other experimental and theoretical methods to provide more detailed structural information.