どの（連体詞：れんたいし)、どれ（代名詞：だいめいし) different part of speech. *「どの」is ALWAYS followed by "noun" (どの＋名詞) e.g. どの動物（どうぶつ)が好きですか？which animals do you like? どの本があなたのですか？which book is yours? *「どれ」is NOT followed by "noun" and itself can be subject. e.g. どれが好きですか？which do you like? どれがあなたの本ですか？which is your book? Another (exceptional) example, when you use "how long, how much, how far..", you can use the both of 「どれくらい」and 「どのくらい」　e.g. どれくらい(どのくらい)住んでいますか？ How long are you living?