Field surveys during 2013–2014 indicated the distribution of Cucumber mosaic virus (CMV), Watermelon mosaic virus-2 (WMV-2) and Zucchini yellow mosaic virus (ZYMV) in the major cucumber-growing areas of Lorestan province, West Iran. A total of 249 (48.2%) of 516 symptomatic cucumber samples were found to be infected. According to the ELISA, viruses in decreasing order were WMV-2 (24.2%), CMV (14.7%) and ZYMV (10%). Moreover, among the 29 positive weed samples with above-mentioned viruses, Sonchus oleraceous and Malva sp. for CMV and Bryonia dioica for ZYMV were found as new natural hosts in Iran. Some weed isolates were more analysed using biological and molecular assays. Using recombination analysis, a tentative breakpoint was found in N-terminal of coat protein of ZYMV-Bd isolate. This isolate is more distinct from the other Iranian ZYMV isolates and fall into group II. However, all Iranian isolates belonged to group I which was divided into two subgroups, IA and IB.