Chronic obstructive pulmonary disease and lung cancer are diseases associated with smoking tobacco cigarettes. Smokers find cessation difficult. To determine whether smoking the Twisp electronic cigarette (e-cigarette), containing nicotine in a vegetable-based glycerine substance, would reduce carboxyhaemoglobin (COHb) levels in regular cigarette smokers by (i) comparing arterial and venous COHb levels before and after smoking the Twisp e-cigarette for 2 weeks; and (ii) evaluating changes in participants' perception of their health and lifestyle following the use of Twisp e-cigarettes. A single group within-subject design was used where tobacco cigarette smokers converted to Twisp e-cigarettes for 2 weeks. Prior to using the Twisp e-cigarette and after using this device for 2 weeks, arterial COHb, venous COHb and venous cotinine levels were determined. Additionally, the participants were asked to complete a questionnaire outlining their perceptions on health and lifestyle. Thirteen participants of median age 38 years (range 23 - 46) with a smoking median of 20 cigarettes/day (range 12 - 30) completed the study. COHb levels (%) were significantly reduced after smoking Twisp e-cigarettes for 2 weeks (mean ± standard deviation (SD) arterial COHb before 4.66±1.99 v. after 2.46±1.35; p=0.014 and mean ±SD venous COHb before 4.37±2.1 v. after 2.50±1.23; p=0.018). There was excellent agreement between arterial and venous COHb levels (intraclass correlation coefficient 0.916). A decrease in cotinine levels (p=0.001) and an increase in oxygen saturation (p=0.002) were also observed. The majority of participants perceived improvements in their health and lifestyle parameters. Smoking the Twisp e-cigarette may be a healthier and more acceptable alternative to smoking tobacco cigarettes.