Extensive development of the light-emitting diode (LED) devices on the basis of LED matrix offers capabilities to occupy LED an increasingly important place for the street and industrial lighting as more reliable and energy-efficient. However, there are not enough experimental data on the optimization of the cooling systems for LED devices. Traditionally, the cooling systems for LED devices are designed with even pitch of LED locations on the radiator’s surface. By the increase of LED power the radiator’s surface and the distance between the LED locations grows correspondingly. It results in the increase of a mass and size the LED device. This paper presents some designs of two-phase thermal control systems for the LED cooling on the basis of conventional thermosyphon (TS), loop thermosyphon (LTS) and heat pipe (HP) and studies the experimental data, which were investigated for the two-phase systems considering the gravity influence. The presented results include: • Some designs of the two-phase systems for the LED cooling. • Start-up characteristics by low, high and intermediate powers. • Power cycling (monotonic and random) and sink temperature cycling behavior. • Temperature drop and temperature oscillations.