The structural design of light-weight lattice observation towers intended for general public use is mostly based on previous experience and mainly considers the wind loads. The most likely reason is a lack of understanding how these structures perform dynamically under human induced walking loads. The paper presents experimentally obtained geometrical and modal parameter ranges of typical light-weight lattice observation towers and the levels of their response to human walking loads. The paper investigates the sensitivity of tower to vibration caused by various walking harmonics and loading scenarios, the influence of visitors group size on the tower response and there are proposed a tentative limit to the maximum ac-celeration level of structure to ensure comfort for the tower visitors.