The article touches upon the change in political parties' structural and organizational characteristics in Western countries in the XX and XXI centuries. We pay particular attention to such aspects as structural party units and their evolution, the development of intra-party democracy, party membership, and its change. The views of the fathers of party science on these problems are investigated. We analyse a party discourse of the problem of intra-party democracy and participation. Changes in the models of intra-party democracy are investigated through the prism of the transformation of political parties' historical types, such as elitist, mass, inclusive, cartel, and cyber parties. The factors stimulating the democratization of the inner-party life of Western parties are shown. We offer generalized verbal models of intraparty democracy in various types of parties. Special attention is paid to the structural features of cyber parties and the influence of information and communication technologies on the internal structure and change of behavioural strategies of traditional political groups. Changes in the membership of parties, their status in traditional and new political parties are shown. The ambivalence of the tendency to reduce the number of members for party organizations is noted. The conclusion is made about the importance of preserving traditional elements of internal organization for modern political parties.