E-governance is the application of information & communication technologies to transform the efficiency, effectiveness, transparency and accountability of informational & transactional exchanges with in government, between Government & Government agencies of National, State, Municipal & Local levels, Citizens & Businesses, and to empower citizens through access & use of information. Governments deal with large amount of data. To ensure that such data is put to an effective use in facilitating decision-making, a data warehouse is constructed over the historical data. It permits several types of queries requiring complex analysis on data to be addressed by decision-makers. This Paper deals with scope and use of data warehousing & Data mining in all the dimensions of e-governance like Government to Citizen (G2C) Citizen to Government (C2G), Government to Government (G2G) Government to Business ,Government to NGO (G2N).T heir are many methodologies used to increase the efficiency of E-governance . Three complimentary trends are Data warehousing, OLAP ,Data mining. By using these techniques we find that data warehousing is very helpful in analyzing Current & Historical data, finding useful pattern & support decision strategies .OLAP is useful in solving complex queries & views , interactive online analysis of data . Using Data mining technique & algorithm, automatic discoveiy of pattern & other interesting trends are found out.