Each geometrical form of room is characterized by a certain specific form of free path length distribution. Its shape can be calculated using the ray-tracing analysis. In the global form of the distribution curve, some characteristic shapes can be recognized which are consequence of room geometrical form at micro and macro level. The distribution of free path length can be quantified by some statistical parameters, such as mean value, relative variance, different momentum, etc. Value of all these parameters is dependent of the room geometrical form and nature of reflections at boundary surfaces. In this paper the possibility to use the free path length distribution in prediction and analysis of a room acoustic response is discussed. Variations in the distribution shape and calculated values of its statistical parameters induced by variations in the reflection process are also shown.