Trstenik is located in the municipality Lanišće, in Istra County at an elevation of 697 meters above sea level and it covers the area of 10.04 km² (3.88 sq. miles). According to the 2011 census report, there were 4 inhabitants. It is entirely populated by Croats. Nearby places: Klenovšćak, Rašpor, Kropinjak, Dane, Prapoće, Vodice, Račja Vas, Brest, Slum and Krkuž.