In modern society, sleep deprivation is a common problem, which has a negative impact on health and cognitive functions. To reduce its impact and optimize performance, a short daytime nap is suggested. However, individual stability of the daytime sleep structure, which is necessary for developing recommendations, has been poorly studied. In the study, we investigated the stability of daytime sleep architecture after reduced nighttime sleep in medical students. 44 subjects napped three times during the day in a 90-minute period. In 129 out of 132 recordings, falling asleep was achieved, in 88 – the third stage of sleep, in 43 – paradoxical sleep. A pronounced stability (intra-class correlation coefficient over 0.6) of the duration of the first and second stages of sleep, sleep duration and the number of awakenings was shown. The parameters of the third stage of sleep and paradoxical sleep were unstable. Subgroups with stable and unstable sleep latencies can be distinguished, and for the group with stable sleep latency, the proportion of awake time after sleep onset is also stable. Based on these data, we can talk about developing recommendations for the optimal individual duration of daytime sleep, which should include only the first and second stages of sleep for optimal results after awakening.