Electricity distribution networks are capital intensive systems and timely investments are crucial for long-term reliability of their service. In coming years, in the UK, and elsewhere in Europe, many networks are in need of extensive investments in their aging assets. Also, aspects of energy policy concerning climate change, renewable energy, energy efficiency, demand side management (DSM), network energy loss reduction, quality of service standards, and security of supply require active, flexible, and smart networks that can be achieved through investments. This paper is a chapter in the forthcoming book "Jamasb T. and Pollitt, M. G. (2011) Eds., The Future of Electricity Demand: Customers, Citizens and Loads, Cambridge University Press: Cambridge" and describes a network investment assessment model developed as a tool to identify and assess the investment requirements of distribution networks. A broadening of the scope of network investments to include demand-related measures that can reduce the need for investments.