The paper illustrates the developments in rules and design lifecycle of modern cruise ship, resulting from the cooperation between industries and classification societies. Fincantieri S.p.A. experience together with Lloyd's Register and RINA technical background, worked side by side in order to overcome not harmonized rules and regulation not specific for this type of ships. Latest IACS example in Common Structural Rules for Bulk Carrier and Oil Tankers development combined with understanding of cruise ship peculiarities have been the basis of the present work. Results of cooperation have been the development of two direct analysis procedure (LR Structural Design Assessment, Procedure for Primary Structure of Passenger Ships, 2017; RINA Guide on Complete Ship Model Calculation of Passenger Ships, 2017), a guideline (LR Ship Rules applicable to Modern Passenger Ships, 2017), and the monitoring of the effects of their application on new buildings. The obtained proposal of harmonized rules and specific regulation highlights the importance of an active role of industries in the rules development that nowadays must be oriented to modern ship business.