FIELD: organic chemistry, chemical technology. SUBSTANCE: invention relates to new method for preparing mixture of 2-hydroxybenzoic acid and 4-hydroxybenzaldehyde or their derivatives, in particular, to method for preparing 3-methoxy-4-hydroxybenzaldehyde (vanillin) and 3-ethoxy-4-hydrxoybenzaldehyde (ethylvanillin) wherein mixture of phenolic compounds one of that is compound (A) comprises formyl or hydroxymethyl group at position 2 and other compound (B) comprises formyl or hydroxymethyl group at position 4 and corresponding to the general formula (IIA) 
and (IIB) 
wherein Y1 and Y2 are similar or different and mean one of the following groups: -CHO, -CH2OH;; Z1, Z2, Z3 are similar or different and mean hydrogen atom, radical C1-C4-alkyl, C2-C4-alkenyl or linear or branched C1-C4-alkoxy-group, radical phenyl, hydroxyl, halogen atom. Method involves selective oxidation wherein formyl or hydroxymethyl group at position 2 in compound (A) is oxidized to carboxyl group and, possibly, hydroxymethyl group of compound (B) at position 4 is oxidized to formyl group. Oxidation reaction is carried out in the presence of a base taken in the amount from 2 to 10 moles per mole of phenolic compounds (IIA) and (IIB) and a catalyst based on palladium and/or platinum that results to preparing a mixture of 2-hydroxybenzoic acid and 4-hydroxybenzaldehyde or their derivatives. Method allows using inexpensive reagents. EFFECT: improved preparing method, reduced cost of method. 39 cl, 3 ex
