Flax fibers coated with two types and various amounts of silicones are used to make flax-polyurethane composites. Coating conditions have been found to affect strongly the composites properties. The effect of these two types and different amounts of silicone on the impact toughness, flexural strength and modulus, dynamic modulus and loss-energy and notch sensitivity is determined. These properties are compared with results of composites with a strong fiber-matrix adhesion.