The aim of this study was to compare the etching pattern of two of the most commonly used etching techniques: the self-etching primers and phosphoric acid. 24 extracted premolars extracted for orthodontic reasons were assigned in two groups: group A–treated with self etching primer, group B–treated with 37% phosphoric acid. Conditioners were applied according to the manufacturer’s instruction. Specimens treated with self-etching primer were washed with alcohol and acetone, the ones treated with phosphoric acid were rinsed with water. Each specimen was examined under a scanning electron microscope. Results: the etching pattern of self-etching primer showed a moderate demineralization with holes and scratches. A more aggressive demineralization of the prism cores were observed on specimens treated with phosphoric acid, both interprismatic and prismatic enamel being dissolved.