The paper discusses the results of investigations of two different variants of miniature loop heat pipe (mini-LHP) with a length of heat transfer of about 0.5m and cylindrical evaporators with a diameter of the zone of heat-load supply of 6 mm and length of 40 mm. The transportation lines in both cases were made of stainless steel in the form of capillaries with an inner diameter of 1 mm. Ammonia was used as a working fluid. The wicks were made of titanium with pore radius of 3.5 and 4.2 μk. The main difference between the two LHPs consisted in the construction of their evaporators. In one of the variants a higher heat-transportation capacity (up to 50W) was provided, but there were problems with the start-up and operation at an unfavorable orientation in the gravity field. The other LHP variant, with a lower heat-transportation capacity (up to 20W), demonstrated a reliable start-up and stable operation at any orientations.