Diagnostic bias leading to diagnostic errors is a common occurrence for all clinicians but every one of us can be blind to it and its consequences on our patients, our clients and ourselves. Examples of diagnostic bias include availability bias, anchoring bias, framing bias, confirmation bias and premature closure. In this lecture we will discuss the types of diagnostic bias that can occur in clinical practice and how they can affect clinical decision making using examples from medical cases and diagnostic imaging as well as steps that can be taken to reduce diagnostic error.