Background: The paper presents changes in the electromagnetic field intensity in a school building and its surrounding after the mobile phone base station installation on the roof of the school. Material and Methods: The comparison of EMF intensity measured before the base station was launched (electromagnetic background measurement) and after starting its operation (two independent control measurements) is discussed. Results: Analyses of measurements are presented and the authors also propose the method of the electromagnetic field distribution adjustment in the area of radiation antennas side lobe to reduce the intensity of the EMF level in the base station proximity. The presented method involves the regulation of the inclination. Conclusions: On the basis of the measurements, it was found that the EMF intensity increased in the building and its surroundings, but the values measured with wide margins meet the requirements of the Polish law on environmental protection.