This Feliway diffuser was recommended to me by a behavioral veterinarian specialist. I have a three year old cat and 3 cats that are just over a year. The three year old cat is used to being by herself, so the addition of the three young cats was a very shocking experience for her. She does not care for them, but she would not harm them either. The fact that there are three of them has her constantly looking in every which direction for them, and she gets agitated at the sight of them. She will wake out of a sound sleep is she hears a noise coming in her direction, so that's why we took her to the vet. Ultimately, we wanted her to be able to be around the kittens calmly and not feel like she was under attack. The vet recommended Feliway diffuser in a room where she feels the most safe and spends the most time, so we made her sort of her own bedroom. At first we attributed the fact that she was sleeping much more to the fact that the diffuser was working. She does seem more calm as the diffuser works, but it only lasts for just over a month. At the vet, this diffuser and replacement is $30, a steep payment to make for something every month. She is still a little anxious, but it seems to work. I wish it was cheaper, but the room diffuser does seem to help make her calmer.