According to Immanuel Kant consequences do not matter, as opposed to utilitarianism in which consequences matter. The Kantian view focuses on the motivation for performing an act with total disregard for the consequences. In opposition to this view, utilitarianism makes ethical decisions about an act based the consequences that the action will bring. For a person who uses the Kantian theory, they believe that the only pure good is human reason without any regard to the consequences. This human reason as discussed by Kant should be without influence of emotions or desires. As opposed to the utilitarian view, that states that the motives of an action are not important, just the consequences. A purely good act, as defined by Kant's theory would be performed because of obligation to the categorical imperative. However, according to utilitarianism a good ethical decision is measured by the amount of happiness that the act creates. This basic difference between Kant and John Stuart Mill's utilitarianism can also be demonstrated in terms of deontological vs. teleological ethics. .
Teleological ethics, which focuses on the end results of an action, can be criticized because it fails to address the instance of someone who really does try hard, with good motivations, but whose end results are not of the greatest good. This brings us to deontological ethics, which focuses on the intentions and motivations of an action. Critics have pointed out, that in order to tell what peoples motivations are, you need to see the end results. This shows the separation between Kant's deontological ethics and Mill's teleological ethics.
Another way to decipher between Kant and Mill is in terms of the difference between Kant being a rationalist, and Mill being an empiricists. Kant stresses a prior knowledge, which is gained apart from sense experience. In contrast Mill as an empiricists, believes all knowledge is obtainable through sense experience.
