A process for obtaining (nitroxymethyl)phenyl esters of salicylic acid derivatives of formula (I) wherein R1 is the OCOR3 group characterized in that it comprises the following steps: a) reaction of a halide of a salicylic acid derivative with hydroxybenzylacohol in the presence of a base: b) nutration of the obtained product in anhydrous conditions by a mixture of nitric acid with a different inorganic acid, or an organic acid, or an anhydride of one or two organic acids: c) recovery of the final product.