Not all Christmas trees are safe for cats. Some trees may contain chemicals or other substances that can be harmful to cats if ingested. Additionally, some types of trees can be a choking hazard if the branches are sharp or break off easily. It's best to choose a tree that has smooth branches and no toxic substances. Artificial trees made of plastic or other synthetic materials are also safe for cats. Just be sure to keep any decorations or ornaments out of reach, as they could also pose a danger.