Deflector for cathode-ray tube comprising a pair of horizontal deflection coils (3) and a pair of vertical deflection coils (4), the two pairs being in the shape of a saddle and isolated one from the other by a separator (2), a frustoconical shaped ferrite ring (5) at least partially covering the deflection coils, the deflector being characterized in that it includes to the rear of the deflection coils, between the horizontal and vertical deflection coils, four field shapers (20) placed symmetrically with respect to the axes of symmetry of the deflector. These shapers are placed so as to increase the amplitude of the second harmonic of the potential of the vertical deflection field without affecting the fundamental of the said potential in order to act on the phenomena of coma appearing on the horizontal edges of the image formed on the tube screen.