This paper reports on the convenient one-step synthesis of hollow polymer nanocapsules by miniemulsion polymerization of different monomers in the presence of larger amounts of a hydrophobe. The idea of the procedure is that the hydrophobe and monomer form a common miniemulsion, whereas the polymer is immiscible with the hydrophobe and demixes throughout polymerization to form the hollow polymer structure surrounding the hydrophobe. The primary objective of this work was to study the effect of different monomers and monomer mixtures, of the type and amount of surfactant, and of the hydrophobe on the morphological characteristics of the polymer/oil composite particle, using dynamic light scattering, scanning and transmission electron microscopies, and atomic force microscopy. It was found that the structure can be adjusted to cover the whole range from independent particles over partially engulfed structures to structurally integer nanocapsules of high uniformity.