Cosmetic composition comprises an organic compound of silicon, and an additional component like polymers, hydroxyl solvents, surfactants or fatty substances, in a medium. Cosmetic composition comprises an organic compound of silicon of formula (R1O) x(R2) ySi-(A) p-CH=O or (R1O) x(R2) ySi-(A) p-CH(OR3)(OR4) and an additional component like polymers, hydroxyl solvents, surfactants or fatty substances, in a medium. R1, R2 : hydrocarbon chain (optionally carry heteroatoms, optionally interrupted or substituted with groups e.g. ether, ester, amine, amide, carboxyl, OH or carbonyl), preferably 1-4C alkyl x : 2-3 y : 3-x p : 0-1, preferably 1 A : a divalent 1-20C alkene (optionally interrupted or substituted with esters of 1-30C alcohol, amine, carboxyl, alkoxysilane, 6-30C aryl, OH or carbonyl), 1-4C alkene and R3, R4 : H or hydrocarbon chain (optionally carry heteroatoms, and optionally interrupted or substituted with groups e.g. ether, ester of 1-20C alcohol, amine, carboxyl, alkoxysilane, 6-30C aryl, OH or carbonyl or an aromatic or optionally heterocyclic ring (optionally substituted with 3-20C ester, amine, amide, carboxyl, alkoxysilane, OH, carbonyl or acyl)). An independent claim is included for a process of structuring the hair comprising applying the composition to the hair, exposing the hair with the composition for more than 30 minutes, preferably more than 15 minutes, and structuring the hair.Composition cosmétique comprenant, dans un milieu cosmétiquement acceptable, au moins un composé organique du silicium de formule (R1O)x(R2)y - Si - (A)p - CH=O (1) ou de formule (R1O)x(R2)y - Si - (A)p - CH(OR3)(OR4) (2) où R1, identiques ou différents, et R2 représentent chacun indépendamment une chaîne hydrocarbonée saturée ou insaturée, linéaire ou ramifiée, contenant éventuellement un ou plusieurs hétéroatomes, éventuellement interrompue ou substituée par un ou plusieurs groupes choisis parmi les groupes éther, ester, amine, amide, carboxyle, hydroxyle et carbonyle,
