In non-invasive mechanical ventilation, the mask interface selection and design are the first physical contact with the patient and the more relevant determinant in their tolerance and response. There are a great number of designs and studies that focus on this topic. However, there is no practical book that incorporates deep analysis, rational physical determinants and patients' responses. This book aims to offer comprehensive expert review chapters on the most significant recent developments in the field of mask interfaces for non-invasive mechanical ventilation, detailing the technology, practices and clinical implications in pulmonary and critical care by providing clear insights and interpretations. Chapters are intended to serve as a reference to those involved in technology, mask selection and patient interaction to properly deliver non-invasive ventilation (incorporating comfort, gas exchange, work of breathing, lung physiology, and interactions of positive pressure) in treatment of acute and chronic respiratory disorders. This aims to offer physicians and researchers a key cornerstone book to understand the basic technology of non-invasive ventilation interfaces and non-invasive ventilation response.