The role of the safety factor (q) and magnetic shear (s) in the formation of Internal Transport Barriers (ITBs) has been shown to be important in several tokamaks [1-5]. Recently JET experiments have been dedicated to the control of ITBs by optimizing the current profile [6]. This paper presents a comprehensive analyses of drift wave stability of JET plasmas with magnetic shear reversal. In the discharges analyzed, LHCD was applied to form a hollow current profile. The stability analysis has been carried out with the linear gyrokinetic code KINEZERO [7,8]. The paper is organized as follows. The next section focuses on the very moment of the ion ITB triggering and puts in evidence the crucial role of the current profile. In the third section the development of the ITB is addressed. In this phase the ExB shearing is essential for allowing the peaking of the ion temperature. In the fourth section the comparative effects on the linear stability of s and the normalized pressure gradient (alpha) are studied when the ITB is fully developed. The effect of the reversed current profile on the instabilities spectrum and the behavior of each kind of particles is investigated in section five.