Polymer-stabilized liposome systems and non-polymer-stabilized (conventional) liposome systems were investigated for particle size, lipid association, micropolarity, and migration of a fluorescent probe between lipid bilayers. The size difference between the two types of liposome systems prepared with identical procedure was determined using light scattering method. NMR spectroscopic analysis using deuterium-labeled lipids showed that under the set conditions all lipids in both polymer-stabilized and conventional liposome systems become associated. Environmental micropolarity assessment of pyrene showed that the probe localizes within the lipid bilayers of both polymer-stabilized and conventional liposome systems. Further investigation revealed that the bilayers of both systems were mobile enough to permit migration of the probe into neighboring unlabeled liposome bilayers.