The present invention relates to process for cracking a hydrocarbon feedstock in a steam cracker unit, comprising the following steps of: feeding a hydrocarbon feedstock to a first hydrocracking unit, feeding the hydrocarbon feedstock thus cracked to a separation unit for obtaining a stream high in paraffins and naphtenes, a stream high in heavy aromatics and a stream high in mono-aromatics feeding the stream high in paraffins and naphtenes to a second hydrocracking unit, wherein the process conditions in the first hydrocracking unit differ from the process conditions in the second hydrocracking unit, separating the stream thus hydrocracked in the second hydrocracking unit in a high content aromatics stream and gaseous stream comprising C2-C4 paraffins, hydrogen and methane, feeding the gaseous stream to a steam cracker unit.