Polymer/clay nanocomposites consisting of a polymer matrix and a dispersed montmorillonite clay (MMT) were discussed. Use of MMT as filler for thermosetting and thermoplastic polymers improves rheological, structural and thermal properties of the resulting materials. Aminoacids, alkylammonium ions, silanes, imidazole salts and crown ethers were characterized as dispersion facilitator's modifying the MMT structure. The polymer matrices discussed include Polyamide 6, polyimides, epoxy resins, polystyrene and polypropylene. Resulting composites characterized by XRD and TEM. Flammability and thermal properties of the nanocomposites are of special importance. Combination of excellent barrier properties and transparency has led to wider application of the polymer/MMT nanocomposites in packaging.