There are cities that have grown to the point that they can swallow up many cities of varying areas and population size. Some of these cities are integrated with the urban settlements within the Mega city through the integration of services and activities distribution, some of them are independent on their own by containing jobs and activities necessary and sufficient for the livelihood of their residents, which reduces dependency on other urban settlements, even those neighboring them. There are also cities that depend completely or partially on neighboring communities and cities, the functional performance of these swallowed up cities varies according to their integration, independence, or dependency, even though they exist in one megacity environment that includes them. The research aims to study the urban functional performance of planned cities within the major city that includes them, to identify the extent to which the quality of functional performance of cities has been achieved within the framework of applying and realizing the concepts of sustainability and the principles of smart cities, As well as identifying the extent of the independence of these cities or whether they follow the function of the major city, making them a satellite city or integrated with the urban settlements within the city, and thus comparing the functional performance of each type and knowing its pros and cons. As well as reaching the best and most appropriate of the three types (independence, dependency, or integration) to use it as a model that can be followed for new city planning in Egypt.