Knowledge Management (KM) continues to develop as an emerging discourse within business management. The area is eclectic in nature and covers systematic management of knowledge, of all kinds, within all levels and types of organisations. However, the majority of studies, in common with other emergent business philosophies, are focused on larger organisations where, for example, readily available, somewhat unlimited resources is an underlying assumption. In contrast KM investigation within Small Medium Size Enterprises (SMEs) tends to focus on specific cases with no key trends identified for KM adoption across the sector. Considering the downturn in the current economic climate empirical research to identify key factors common to all organisations, irrelevant of size is necessary, supported by both empirical findings and case experiences. This paper presents the findings from a large-scale empirical investigation conducted in 2009 with a number of UK companies. The purpose of the research was to investigate how KM implementation can influence organisational sustainability, development and maturity in both small and large companies. This research builds on a ten-year project investigating KM implementation within UK companies employing both quantitative and qualitative approaches. The research considers how KM affects internal organisational processes, to strengthen the link between operations and strategy, resulting in better decision maker, faster products to market, better service quality and enhanced customer loyalty. Core aspects of technological application, information management, employee emancipation and process improvement are considered providing a framework for KM adoption and uptake. This paper compares KM implementation and development between large corporations and SMEs to ascertain if organisation size matters. The paper commences with a brief literature review outlining key elements which effect KM implementation. Based on the MeCTIP model and utilising the 'Benchmarking KM' online survey tool, empirical analysis of KM implementation and development with a large sample of UK companies is undertaken. Initial statistical analysis finds that KM can contribute to organisational sustainability, development and maturity by a number of internal organisational factors, such as technology, information and people. As organisations are receptive to influences beyond their boundaries, changes in the macro-environment tend to affect both organisational climate and internal technical climate, which has a knock-on effect for KM adoption and implementation. This paper compares results for SMEs and larger firms.