Experimental setup for measuring critical heat flux in nucleate boiling of dieletric fluid FC-72 was made. Critical heat flux was measured on metal ribbon heater, which was positioned horisontaly and oriented verticaly. Different processed heated surfaces were analized on critical heat flux. Measurements of wettability on processed surfaces were made for contact angle and speed of wettability. Critical heat flux in nucleate boiling of FC-72 was measured between 114,1 and 196,9 kW/m2, contact angle was between 60,0 and 75,1 °, speed of wettability was between 0,45 and 0,62 mm/s.