PURPOSE: To obtain the title composition which can impart higher water repellancy by blending a specific amount of inorganic finely divided particles having hydrophobic surfaces and which have a specific average particle diameter and a specific surface area with a solution containing a silicone or fluororesin compound.

CONSTITUTION: The title composition is produced by blending inorganic finely divided particles which have a specific surface area of 50 m2/g or more, an average particle diameter of 4 μm or less and hydrophobic surfaces with a solution comprising a silicone or fluororesin compound so that the ratio of the particles to the solid component in the solution may be 10-40 wt.%. On the surface of the base material coated with the above composition, because of the fine irregularities formed by the inorganic finely divided particles, in addition to the water-repellent effect of the silicone or fluororesin, the contact area of the surface with waterdrops becomes small and the water repellancy becomes remarkably high. Also, by applying the composition to the surface of platelike fins of a heat exchanger, the condensed waterdrops roll down, so that the fin area can be increased by decreaseing the distance between the platelike fins, and therefore the thermal efficiency is improved.