The way we think determines both how we feel and how we behave. The way we think about ourselves, other people and our place in the world has a direct influence on our emotional state and our behaviour. Consequently by changing the way we think we can positively influence our mood and how we respond to situations. This is the premise behind Cognitive Behaviour Therapy (CBT) which has become the most effective psychological treatment available for a range of emotional and behavioural problems including depression and anxiety. A thought diary is designed to help people record and change the thoughts that cause emotional and psychological distress. The Thought Diary Pro is the advanced version of the Thought Diary, and allows the identification of thinking errors (also known as 'cognitive distortions'), and the the modification of our unhelpful thoughts into more productive ways of thinking. By challenging the thoughts and beliefs that cause discontentment, dissatisfaction and other emotional and behavioural distress, we can improve our mental health and can change the destructive or adverse behaviours we may engage in as a result of our negative thoughts. Thought Diary Pro is designed to be the second step in changing our thinking patterns by helping individuals identify the thinking errors that they engage in, and thereby helping change these thoughts. The effect of modifying these thought can reduce the negative emotional and behavioural consequences of experiencing these negative thoughts. Similar to the Thought Diary, the Pro version was designed by an experienced clinical psychologist and CBT therapist who believed that these tools should be available in the most accessible form for individuals to use in todays fast technological world. It can be used by people either in therapy as a useful adjunct to the treatment, and there is a feature that allows the Thought Diary to be emailed straight to their therapist. However, it can also be used by those individuals who are embarking on a self-guided course of CBT.