Electronic cigarettes (e-cigarettes) are alternative tools that are developed to help the smokers quit smoking which is considered a major modifiable risk factor of cardiovascular disease. The aim of this study was to assess Cardiovascular Disease Patients' Knowledge Toward Electronic Cigarette Smoking Design: A descriptive analytical design was used. Setting The study was conducted at cardiac outpatient clinic in Menofia University Hospital Sample: A purposive sample technique was used to recruit 368 patients. Inclusion criteria: The age from 18 to 55 years and smokers Data collection tools: Two tools were used: 1- Structured interviewing questionnaire. 2- Medical record tool: Results: The study showed that, more than two thirds of the studied patients had unsatisfactory level of total knowledge about electronic cigarette smoking. More than one third of the studied patients had information about electronic cigarette from internet and social networking sites. Conclusion: There was highly statistically significant difference between age, gender and educational level with total level of knowledge (P=<0.01). Recommendations:      Development of educational health programes to raise awareness of smokers, cardiovascular disease patients and public about e-cigarette smoking  through mass media, social media, clear language booklets and simplified brochures.