There are two important types of parasitic worm in dogs - roundworms and tapeworms. Roundworms can grow up to 15 cm long and are white in colour. As their name suggests they are round (like string), whereas tapeworms are flat (like ribbons). Tapeworms can grow up to 60 cm long. Both roundworms and tapeworms live in the dog's intestines along with two other types of smaller worm (similar to roundworms) called whipworms and hookworms. However, these rarely affect dogs in the UK. In some countries there are parasitic worms that can live in the dog's lungs, heart, stomach or bladder but these are rarely seen in Europe.