This thesis explores the term ‘walkability’, how itis understood, measured and what role it plays in neighbourhood mobility and physical activity behaviours. Two groups are of interest in this study, the professionals tasked with planning and designing neighbourhoods and the residents who live within these environments. This thesis outlines a mixed methods project comprising of a literature review and four studies. The literature review analyses the concept of walkability with particular focus on identifying and collating neighbourhood meatures associated with walking behaviour and how they are measured. An online survey was used to understand level of ambiguity, or agreement, between relevant professions on the elements of walkable environments in study one. Study two further explores walkability using a phenomenological study with a select group from study one. In study three, a novel site selection process, based on the findings of the previous studies, was used to identify high and low walkable areas in the GreaterDublin Area. Study four describes a cross sectional study which was undertaken to investigate the environmental perceptions and behaviours of residents living in identified neighbourhoods. Univariate analyses were carried out on correlates of interest to compare the four area catagories; high walkable deprived, high walkable not deprived, low walkable deprived and low walkable not deprived. In conclusion, ambiguity exists in both the understanding and measurement of walkability. Neighbourhood walkability is dependent on the physical environment, the social environment, and how both are perceived. They key elements for consideration are: (i) scale, (ii) permeability, (iii) a liveablevillage centre and (iv) the streetscape with particular emphasis on transparency and no visual disorder. A model was proposed for future multivariate analysis which considers the many influential correlates of walkability.