The conformations of the molecules of DNA-surfactant complexes in dilute solutions and on the atomic smooth surfaces of mica and highly oriented pyrolytic graphite were comparatively studied by the methods of isothermal diffusion, electric birefringence, and atomic force microscopy. The DNA-surfactant complexes were deposited onto the substrates from a chloroform solution. The number of particles of the DNA-surfactant complex on the substrate was changed by varying the concentration of the initial solution within three orders of magnitude. The particles of a shape close to ellipsoidal, 25-70 nm in diameter and 2-4 nm high, were observed at the lowest concentration of DNA-surfactant solution on the mica substrate. The shape and size of these particles correspond to those of a single DNA-surfactant complex, calculated from its translational diffusion coefficient and the time of orientational relaxation in dilute solutions. An increase in the number of molecules deposited onto the substrate leads to an increase in the characteristic sizes of DNA-surfactant complex particles observed by the atomic force microscopy. This may be associated with the aggregation of DNA-surfactant complexes.