The paper analyzes changes within the planning system of the Cuban Republic that took place in the context of changing methodological base of planning while entering the Council for Mutual Economic Assistance (Comecon). The end of 1960s was marked by a radicalization of the methods of socialist construction: the system of economic register was applied and diminished the role of the category of value. This led to an economic imbalance, loss of control over the costs of production, deterioration of motivation to labour, etc. In addition, the plan of 10 million tons of sugar production in 1970 was not achieved. These factors prompted the Cuban leadership to reconsider the planning methodology and the development strategy, and to rely heavily on the experience of the USSR. Thus, the Soviet Gosplan experts started consulting their Cuban colleagues from the Central planning committee to a greater extent. However, sometimes there was misunderstanding between the parties, which is revealed in the conversations between the Soviet Gosplan head N. Baybakov and Cuban leader F. Castro. Carlos Rafael Rodríguez played a significant role in political economy diplomacy, and gave a speech as a representative of Cuba at the XXVI Comecon session when the country was accepted to the organization. Entering Comecon spurred the process of changes within the Cuban economic policy: the category of value recuperated its significance within the planning system, new annual plans were based on the value indicators and the input-output models. The midterm planning was also reintroduced due to 5-year plans preparation. Cuba integrated the mechanism of plan coordination with the Comecon countries, while the USSR continued to be its most important partner. Nonetheless, the process was slow: the 1971—1975 five-year plan had not been connected to the Comecon mechanism of plan coordination. Cuba insisted on a special attitude due to its low level of development. Cuban economy reconfiguration under the influence of planning mechanisms of Comecon countries favored consolidation of the new System of planning and direction of the economy approved by the decisions of the first congress of the Communist party of Cuba in 1975.