The author takes into consideration, in the first place, the technological innovations and the employer power of control. Then she describes the right to self-determination of the employee as regards information in the present days juridical systems. In relation to the right to privacy, art. 2 of the Italian Constitution is taken into consideration. In the Spanish Constitution, the roots of the right to privacy are traced in art. 18. Then, the right to self-determination of the employee as regards information is analysed in the light of the EU legislation. In the second part, the essay analyses the Spanish legislation in the area of protection of personal data. Then the author takes into consideration the questionable efficacy of the protective techniques adopted in the pre-contractual phase and during the labour relationship.