Around the world, there are several operational Lightning Location Systems — LLS which produce real-time information about the electric atmospheric activity over a specified region. The performance of these networks is evaluated by means of their location accuracy and detection efficiency. These parameters are functions of several variables including those related to the location and altitude differences between the Lightning Location System sensors. The effect of these variables on the LLS performance could alter its performance increasing their location error, and decreasing their detection efficiency. Typically, these parameters are estimated theoretically; in this work, the information obtained from actual lightning photographs is used to estimate the detection efficiency of one of the Lightning Location Systems installed at present in Colombia (South America), over a highly mountainous region as is the case for the city of Medellín.