Intraperitoneal (i.p) chemotherapy is an attractive approach to treat peritoneally disseminated cancers by delivering therapeutic agents directly to the peritoneal cavity where some disseminated tumors are located. Cationic liposomes (CLs) have been used as a viable delivery carrier for i.p. chemotherapy to improve the peritoneal retention of anticancer agents. However, there are no reports on the fate of CLs following i.p. administration to the peritoneal cavity in the presence of disseminated tumors. We prepared a tumor xenograft murine model of peritoneally disseminated gastric cancer by i.p. inoculation of human gastric cancer cells and followed the fate of either CLs or PEGylated CLs (PEG-CLs) after i.p. injection in the model. I.p.-injected CLs were retained in peritoneal cavity for at least 3 days post-injection as a result of clustering with ascites fluid proteins, mainly albumin, while i.p. PEG-CLs was rapidly cleared from the peritoneal cavity to the circulation within 3 h post-injection. Importantly, i.p. CLs efficiently accumulated in the targeted disseminated tumor cells, but not in other abdominal organs including liver, spleen, and kidney. The tumor selectivity upon i.p. administration of CLs may be associated with the lymphatic drainage system. A lipoplex formulation composed of CLs with short hairpin RNA (shRNA) against luciferase, a model therapeutic agent, suppressed luciferase activity in peritoneally disseminated tumors by 80%, with no cytokine secretion in serum. This suggests that i.p. CLs can efficiently deliver a therapeutic agent to peritoneally disseminated tumors with few systemic adverse events. These results suggest that i.p. treatment with CLs or non-PEGylated lipoplexes may be a promising approach for the treatment of peritoneally disseminated cancers through their ability to selectively deliver therapeutic agents to i.p. target sites with minimal systemic adverse events.