The thesis deals with risk analysis when designing a lightning protection system using the HRN EN 62305 standard. The paper presents a procedure for calculating the risk in the event of a lightning strike on a building that is planned to be protected and the supply line connected to the building or in the event of a lightning strike next to the building in question and next to the supply line, in order to determine the need for protective measures. The calculation procedure includes an estimate of the annual number of hazardous events, an estimate of the probability of damage and an estimate of the amount of losses. The above calculation procedure and risk analysis were carried out on the example of an office building. The conclusion on the necessity of installing a lightning protection system is based on a comparison of the obtained risk results with the acceptable risk values specified in HRN EN 62305.