An internal-combustion engine, comprising for each cylinder: - a combustion chamber; - at least one intake duct and at least one exhaust duct giving out into said combustion chamber; - at least one intake valve and at least one exhaust valve associated to said intake and exhaust ducts (4, 6) and provided with respective return springs that push them towards a closed position; and - a camshaft for actuating the intake valves (7A, 7B) by means of respective tappets; - wherein said at least one intake valve is governed by the respective tappet against the action of the aforesaid return spring by interposition of hydraulic means including a pressurized-fluid chamber facing which is a pumping plunger connected to the tappet of the valve, said pressurized-fluid chamber being designed to communicate with the chamber of a hydraulic actuator associated to said at least one intake valve; - a single electrically actuated control valve (24; 1; 100; 1') associated to said at least one intake valve of each cylinder and designed to set said pressurized-fluid chamber in communication with a discharge channel in order to uncouple said at least one intake valve from the respective tappet and cause rapid closing of said at least one intake valve by action of the respective return spring; - electronic control means, for controlling said solenoid valve to vary the instant of opening and/or the instant of closing and the lift of each intake valve as a function of one or more operating parameters of the engine, said internal-combustion engine being characterized in that the electrically actuated control valve (1; 100; 1') associated to each cylinder is a two-way valve having at least three different operating positions, namely, - a first operating position in which it is completely open; - a second operating position in which it is only partially open; and - a third operating position in which it is completely closed, and in that said electronic control means are programmed for: - keeping said control valve in said third, completely closed, position in operating stages in which said at least one intake valve must remain coupled to the respective cam, - bringing said control valve from said third, completely closed, position to said second, partially open, position or to said first, completely open, position in operating stages in which said at least one intake valve must be uncoupled from the respective cam, the selection between said first position and said second position of the control valve being made as a function of one or more operating parameters of the engine. - a combustion chamber; - at least one intake duct and at least one exhaust duct giving out into said combustion chamber; - at least one intake valve and at least one exhaust valve associated to said intake and exhaust ducts (4, 6) and provided with respective return springs that push them towards a closed position; and - a camshaft for actuating the intake valves (7A, 7B) by means of respective tappets; - wherein said at least one intake valve is governed by the respective tappet against the action of the aforesaid return spring by interposition of hydraulic means including a pressurized-fluid chamber facing which is a pumping plunger connected to the tappet of the valve, said pressurized-fluid chamber being designed to communicate with the chamber of a hydraulic actuator associated to said at least one intake valve; - a single electrically actuated control valve (24; 1; 100; 1') associated to said at least one intake valve of each cylinder and designed to set said pressurized-fluid chamber in communication with a discharge channel in order to uncouple said at least one intake valve from the respective tappet and cause rapid closing of said at least one intake valve by action of the respective return spring; - electronic control means, for controlling said solenoid valve to vary the instant of opening and/or the instant of closing and the lift of each intake valve as a function of one or more operating parameters of the engine, - a first operating position in which it is completely open; - a second operating position in which it is only partially open; and - a third operating position in which it is completely closed, and - keeping said control valve in said third, completely closed, position in operating stages in which said at least one intake valve must remain coupled to the respective cam, - bringing said control valve from said third, completely closed, position to said second, partially open, position or to said first, completely open, position in operating stages in which said at least one intake valve must be uncoupled from the respective cam, the selection between said first position and said second position of the control valve being made as a function of one or more operating parameters of the engine.