Silver halide particles were synthesized in a water-in-oil microemulsion consisting of AOT (sodium bis-2ethylhexylsulfosuccinate)in-heptane Different molecules of thiacyanines were adsorbed on these particles. These molecules can be adsorbed on the particles by two main sites of adsorption: either by an interaction between the sulfur atom and the silver ion or by a Coulombic interaction between the nitrogen atom and the halide ion. To distinguish the two adsorption sites, particles with different excesses of charge have been used. It has been concluded that the adsorption site depends on the structure of the molecules: the sulfur is more reactive in the presence of an electron donor moiety and more for the thiacarbocyanine than for the thiacyanine. The adsorption between the sulfur and the silver ion is also more favorable on the silver bromide particles than on the silver chloride particles.