In April 2013, the Laboratory of Geomatics launched the project under the acronym “Bartek 3D” in cooperation with the Research Section of Students from the AGH in Krakow, Pedagogical University and the Jagiellonian University as well. The main aim of the project is to monitor the biggest and probably one of the oldest trees in Poland - Oak Bartek in Zagnańsk (N 50o59’14”; E 20o38’59”), based on multi-temporal Terrestrial Laser Scanning (TLS) technology. One of the results of the project should be a 3D model of Oak Bartek and detection of the changes in the shape of the tree. Terrestrial Laser Scanning and the traditional forest inventory measurements were performed during the Leaf-OFF season in April 2013 and April 2014 and repeated in Leaf-ON period in July 2013 and October 2014 with using scanners: FARO FOCUS 3D, RIEGL VZ-400, LEICA C10 and RevScan (HandyScan). The results based on TLS technology showed some differences comparing to existing data obtained by traditional measurements for forestry inventory: Height (H) of the tree: altimeter Vertex (Haglöf) H = 29.31 m; HTLS = 28.49 m; Trunk circumference (L) measured with stretched tape: LST = 9.80 m; adjacent along the shape of bark: LT = 13.70 m; TLS measurments: LTLS1/4 = 9.97 m oraz LRevScan = 13.54 m, The average diameter at breast height (DBH130cm) calculated on the basis of 3D basal area of stem DBHTLS1/4 = 3.03 m (DBHT = 3.12 m).