Acrylic and methacrylic acids were esterified with dodecyl, hexadecyl and NAFOL 20(+) (C-av = 21) alcohols. The monomers thus prepared were copolymerized with C-18 alpha-olefin at different molar ratios. The copolymers were purified, characterized and then assessed as cold flow improvers for a high-pour waxy residual fuel oil (RFO) by pour point and rheological measurements. The asphaltene, resin and wax contents of the RFO as well as the carbon number distribution of the wax fraction were determined. The results show that only the polymeric structures with long side chains of NAFOL 20(+) have the potential to decrease the pour point and improve the rheological properties of the fuel oil. The storage stability of the treated RFO is good up to 3 days but then diminishes steadily. The effectiveness of the prepared additives is discussed on the basis of structure in relation to the fuel oil composition.