A funnel of a cathode ray tube includes a yoke attachment portion on which a deflection yoke is mounted so as to deflect the electron beam emitted from an electron gun along horizontal and vertical axis. At least one cross section of the yoke attachment portion, perpendicular to the tube axis, has an inner contour which is substantially rectangular with four sides. The sides are defined by convexities curved toward the tube axis and each having a peak on the horizontal or vertical axis. The inner contour of the cross section faces the electron beam passage region with a substantially constant gap.