The past two decades have witnessed enormous advances in the field of rhinology and sinonasal diseases. Chronic Sinusitis is one of the most common chronic illnesses. The introduction of functional endoscopic sinus surgery in the late eighties has revolutionised the surgical approach to sinus disease. Since that time, endoscopic sinus surgery has become the surgical procedure of choice and has been adopted for training and teaching. Furthermore, the approach to sinus disease has significantly evolved. We have witnessed the introduction of balloon sinuplasty, image guided surgery, multidisciplinary approach and the promotion of evidence based medicine and guidelines. The essence of any surgical technique or any guideline is based on the wealth of knowledge of anatomy and physiology. This book details the explicit anatomy and pathophysiology of the various sinuses. Special emphasis has been made on paediatric sinus diseases since it is a topic that has not been well covered and mandates further understanding. This unique book can form a roadmap for the otolaryngologist in training, medical students practicing otolaryngologist in private or academic sector and paramedical personnel. The target and scope go beyond otolaryngology to attract the attention of any paediatrician, general practitioner or family medicine specialist. The chapters have been well-written not only to detail the importance of each structure and pathophysiological mechanisms, but also to make it easily understandable for all readers at different levels. The authors have been selected from panels of nationally and intellectually acknowledged experts. The wealth of information in this book has exhausted the efforts of brilliant and well-established, experienced and academically prominent leaders in their fields. All chapters are not only written in easy-to-read detailed paragraphs, but are also illustrated with radiographic and surgical figures adding a live interpretation to the abstractive sentences. It is our hope that this text will serve as a comprehensive contemporary guide and reference to all students and practitioners that aim to widen their horizon of learning, revive their illustrative and descriptive memory of knowledge and improve their expertise.